Scosche TA-03 Wiring Kit Noise Mod [Archive] - Forum

: Scosche TA-03 Wiring Kit Noise Mod

08-11-2003, 02:03 AM
Left: Original Scosche TA-03 (came w/BlueBox) <------> Middle: Scosche TA-03HB (harness only/no BlueBox) <------> Right: Best Kits BHA8113 identical to orig TA-03 (search eBay)
Note: orig harness (left) doesn't have a shell covering the pins so it's easy to mod, newer harness (middle) has the extended shell covering the pins making it difficult to mod, and BHA8113 harness (right) is identical to the original TA-03 so GET THIS ONE!

20-Pin Toyota Wiring Harness w/RCA for 2K & Up Premium 8-spkr w/FactoryAmp Mod for:

The Scosche TA-03A & TA-03B Harness
and BHA8113 Harness

(update 1/05: This mod fits 2000 & up GT's & GTS's w/optional Premium 3-in-1 AM/FM ETR/Cassette/CD w/8 spkrs & separate amp)
= click to jump to post about which GT's this will fit & about TA-02 harness vrs. TA-03 = (

(update 7/07: Latest notes on the new TA-03B Harness, BHA8113 harness, Metra TYTO01 harness)
1) Some time ago the original Scosche TA-03 was superceded by a newer TA-03B harness which uses a different connector ( that has an extended shell covering the pins, making it more difficult to mod.

2) When selecting resistor values from the Termination Resistor Table for the newer TA-03B, add +16% to the value from the table, or use the following calculator to find the exact value, substituting 2200 ohms for R1 (the TA-03A uses 1900 phms for R1): Voltage Divider Calculator (

3) There are many wiring harnesses out there which claim to be compatible with the 00-02 / 03-05 Celica's but members have discovered are not compatible. We know the original TA-03 was the easiest to modify and absolutely works, as well as the newer TA-03B, even though it's a bit more difficult to mod. We also know the BHA8113 Harness ( also works, and may still have the original Scosche TA-03 style connector that's easier to work with.

4) Recently members have been asking me about a new "compatible" harness called the Metra TYTO01 ( At this time all I can say is that it looks like it might work with later JBL-equipped vehicles which use the Toyota databus to control Turn-On. Other than that, I don't know yet whether it needs the mod or not. Note: Metra does not list any Celica's in their TYTO01 compatibility table.

(update 8/07: )
1) Confirming: the BHA8113 Harness ( is identical to the discontinued original TA-03 harness, including long pins making it easy to modify compared with the newer Scosche, so I'd recommend you use the BHA8113 instead of the Scosche TA-03B.

2) If your HU only has two RCA outs (L&R) you can use an RCA Y-Cable to connect to the StockAmp's Rear RCA's, but you'll need to roughly double the value of the termination resistors to avoid double-terminating the signals. For example if the table says use 600 ohms, use 1000-1200 ohms instead.


You might think installing an aftermarket head-unit and hooking it up to the existing FactoryAmp would be a piece of cake, esp. using Scosche's TA-03 wiring harness and matching Toyota connector. Not so, and like just about everyone else here who's tried it I got loads of ECU noise, power-window buzz, dimmer buzz, and the worst: alternator whine. After installing and removing my HU about a dozen times trying things, I was about ready to throw that fancy HU out the window and put the stock unit back in, until...

I love my Celica like most everyone here does, and cuz I got so much help from reading the posts on this board, I'm posting this to give a little back. So I hope I do this right...

I'm an electronics engineer, but after re-checking everything it all looked like it was hooked up ok, aw crap. Like everyone else I thought it must be a grounding problem. Well, yes & no. And what's with the blue box Scosche gives you with the switch on the side? I wasn't about to give up because I know how good the stock GTS Premium Stereo can sound, so that FactoryAmp can't be all that bad... so I kept going.

In a nutshell... I found out our GTS Premium 4-channel FactoryAmp has high-impedance inputs with virtually no input termination. This means when you hookup most head-unit's PreAmp Outs (which have virtually no output termination) the RCA cables and the Celica's own HU-to-FactoryAmp wiring harness act like radio antennas picking up every little electrical noise generated by the car. Have you ever stuck your finger on the end of a guitar cable with the amp cranked up? Same thing.

On top of that, the TA-03 has a 1.9k resistor in series with every RCA cable. If you feel the heatshrink, you can feel the resistor inside each cable.

Solution... Terminate the inputs of the FactoryAmp to match the output impedance of the head-unit being installed. Doing this effectively dumps most of the electrical noise picked-up by the RCA's & wires to ground while allowing the higher-level audio signals to pass on to the FactoryAmp's inputs.

Click Here: If you don't see pics (goes to Tripod clone site) ( (updated link: 3/06)
Remove heatshrink from audio pins (notice hidden resistors in black shrink, also 4 new resistors in front
Back of TA-03 showing 4 audio pins - (Red Wire is Right Channel & Top Row is Front)
Unsolder the 4 RCA wires from the connector pins and twist termination resistors onto them before soldering
Add heatshrink tubing (yel) to prevent shorts & add structural support, then tin the ends and solder
them back to the pins
["tin the ends" means melt some solder into each twist first, then when you solder them back to the pins they've
already got plenty of solder so you don't need 3-hands to add more. Use one hand to hold the twist onto the pin
then touch the soldering iron just long enough to make the connection melt back to the pin.]
Add more heatshrink (blu) then twist the ends of the resistors together and tin with solder
Add larger heatshrink to Analog GND wire & solder it to the twisted end of the resistors
After applying heatgun to shrink tubing - (Top Row is FRONT Left & Right)
Completed Mod - tie-wrap all power leads together, then separately tie-wrap all audio & gnd's together
Scosche TA-03 FactoryAmp Noise Fix Mod - Basic Pictorial Diagram & Notes

The output impedance of my head unit is 60ohms at 5vrms, so the 1.9k (1900 ohm) series resistors don't hardly reduce any level and it's easier to leave em in. Basically what you're doing is adding a terminating resistor from each signal wire to ground, closest to the FactoryAmp's inputs. (Ideally you would do this right inside the amp, but this won't be necessary unless you plan on listening to your stereo while driving thru an MRI Scanner or past some military radar dish)

|__________________SCOSCHE SLC-4 "BLUEBOX" SPECS
|____________( comes w/TA-03 Kit - features & notes below )
| * 4-channel HV LINE LEVEL to 4-channel LINE-LEVEL converter
|__( don't need SLC-4 for HU's w/Preamp Outs - Only use TA-03 Conn w/Mod )
| * 4-channel SPEAKER LEVEL to 4-channel LINE LEVEL converter
|__( up to 80 watts max per channel )
|__( use SLC-4 together with TA-03 Conn w/Mod - adjust trimpots on SLC-4 to match levels )
| * Transformer circuit for noise cancellation.
| * Common ground adapter.

So what's with the blue box Scosche provides? Well in an ideal noise-free world you would set the switch to "Line" and plug your RCA's into it and wire the other end into your amp, but if you don't have a HU with high-level preamp outs you can connect your HU's speaker outputs into it (thru the screw terminals) and it will drop speaker-level down to line-level to feed the FactoryAmp. Will you still need to do this mod? Uhm, yeah probably... it's because inside the SLC-4 BlueBox are 4 level-dropping circuits and impedance matching/isolation transformers. What's great about transformers is that they can match the impedance of one circuit to another almost perfectly, plus they can isolate DC path between two devices and only pass the audio signal, but what's not so great is that they can also act like guitar pickups when designed to be connected to high input-impedance amps like ours.

Ever hookup a Scosche SLC-4 BlueBox and wave it around the inside of the dash with the ignition on? Acts like a Theremin doesn't it? That's cuz its transformers are picking up the noise from the data bus running all thru the Celica wiring harness. Ever play with a telephone pickup coil? Almost the same thing.

Notice the TA-03 has 3-ground wires coming out of it. Make sure you connect the ends of the 4 resistors (tied together) to the wire labeled Analog GND in the photos & diagram. The other two GND wires can be tied together and connected to your HU's GND wire. Believe it or not, once you terminate with resistors, your grounding problems will pretty much disappear.

I forgot to mention that when you terminate audio lines with the matching impedance of your HU, your frequency response will probably be restored more closely to what it's supposed to be too. In otherwords if it sounded too bright & tinny before, your bottom end (bass & lows) should come back to life again and you won't have to subtract your treble & max your bass eq settings anymore.

thanks for the help on the board & enjoy your FactoryAmp, I hope it helps...

ps ~ i want to give some credit to EvilED who posted a msg way back in 10-12-2002 about a mod for the factory amp. I found it while searching to make sure the TA-03 Noise wasn't a topic already covered. It just goes to show that doing thorough research pays off if you bother to do it (and no, I didn't find it until it was too late cuz I was lazy too... crap!)

Click Here: EvilED's factory amp mod (

Click Here: If you don't see pics (goes to Tripod clone site) (

Click Here: For a table of Termination Resistor Values and Final Test Results (

Click Here: To jump to post about which GT's this will fit & about TA-02 harness vrs. TA-03 (

Click Here: Wanna hear a simulation of what the Scosche TA-03 Harness sounds like -without- the mod? ( [updated 4/2017: sample mp3 file moved to Tripod]

08-11-2003, 06:22 AM
cool write up, i was actually about to buy an amp to get rid of the noise, but i guess i'll try this mod....
is there any way you can make the pics show?
so far, are there any drawbacks to this mod?

08-11-2003, 07:41 AM
Yeah, host your pics somewhere else besides image station.

I just got rid of my whine, but I did something different. I cut the speaker leads away from the stock amp and hardwired them to my HU, running the front speakers in a series. Unfortunately this destroyed the power in the front speakers, they were really weak and sounded terrible, so then I got an idea... I reconnected the larger front speakers to the stock amp (my HU has both pre-outs and speaker leads) and left the front tweeters and rear speakers connected straight to the HU. This way I keep my power and almost completely remove any whine or humm. If you listen really close there is a slight whine, but the speakers are mid-range only so it's not noticable over any other normal cabin noise. I'm very pleased with the way it's turned out.

08-11-2003, 08:18 AM
Sweet write up. Try taking the .orig out of the link. Oh, and you've got a PM.


08-12-2003, 06:35 AM
Thanks everyone.

01blkgts, nope no drawbacks so far. Before the mod I could tell my bass was missing and the mids & highs were way too loud & out of proportion when my volume control was barely cranked up. Now it's nice & loud while the volume sits right in the middle of its range with plenty left to go plus now the "Loudness" button works like it's supposed to. Just make sure the termination resistors match the HU's output impedance: My HU's high voltage preamp outs are 5v @ 60 ohms, some HU's are 2.5v @ 200 ohms, in that case you'd substitute 200 ohm resistors in place of the 60's that I used.

Sorry about the Imagestation thing, I know it can be a pain. I used to not be able to see stuff on the boards until I finally gave-in & registered. Ever since then I guess it set a cookie in my browser so I automatically get access to pics from their site. I thought about moving them over to a Yahoo account but I'm not sure what their policies are about inactivity & traffic loads.

The pics were originally shot in 1600x1200 by an Exilim w/closeup adapter lens but I didn't want to offend the board by posting Jurrasic-sized pics in the thread so I shrunk them down to 640x480. If there's enough interest maybe I'll upload the monsters to an album on Imagestation and post a link in the thread.

SQ GT-S thanks, I sent you a PM. I tried dropping the ".orig.jpg" but the pics shrank even smaller so I put em back the way they were.

08-12-2003, 06:28 PM
i would really apppreciate it if you can post the pics somehow...

08-12-2003, 06:34 PM
Or just post the links to the pics for those who can't access them...

08-13-2003, 07:46 AM
:werd: just make them links...

08-15-2003, 09:53 AM
The Imagestation thing is weird, on some computers the post comes up w/empty Imagestation boxes instead of pics and on others it comes up with pics even tho those computers have never been registered on Imagestation (no previous cookie).

Anyway, I copied the post to Tripod and put a link to it near the top & bottom of the original post, or you can just click the same thing here:

Click Here: If you see Imagestation boxes instead of pics (

(let me know if the empty Imagestation thing is still happening in the original post and if you like, maybe I'll just hook the pics directly to Tripod instead)

08-16-2003, 08:19 AM
I'm still new at this and plan on installing my system next week. Anways, if I have an aftermarket amp and HU, will I still hear a whine when I install it. Which is a better method? Hardwiring it to the stock harness or buy a new one that is an adapter made specifically for the Alpine(where can I get one that is good).

08-16-2003, 11:40 AM
this should be stickied

08-18-2003, 12:20 PM
Does anyone know how many wire harness there is for the stock radio? Also, is the stock wire harness connected to another wires then goes to the fuse? I'm asking this because my lights dont' work anymore for the stock radio but it still play music though. I might be the grounding because my cig light and my ac control grounding is burn/shorted out.

08-18-2003, 10:28 PM
tripnotic - I don't know if your Alpine HU is terminated inside, but from reading the posts of others on the board likely not. You'll just have to get a Scosche TA-03 kit and try it out. If you get noise you'll definitely need to do the mod.

(please note: this mod is only for the Scosche TA-03 which mates w/Toyota's 8-speaker 4CH premium stereo HU connector)

Technically, if you buy a HU that comes with high-voltage preamp outs (2.5 - 8.0 volts) plus a built-in or external power-amp, the best way to hook it up is to use the HU's own amp which is designed to match it. Of course this means bypassing the factory amp by disconnecting the speaker wires from the amp and splicing into them or running new wires to every speaker. (don't wire your HU's speaker outs across the factory amp's speaker outs - disconnect em from the factory amp)

If you're happy with how the premium factory amp sounds (w/stock or upgraded speakers) but just want to install a different HU, then get the Scosche TA-03 and mod it if necessary.

The last thing you want to do with any decent sound system is to drive a power amp off another power amp. I mention this only because there are products out there like some of the OEM Interface Adapters (aka speaker-to-line level converters including the bluebox that came with the TA-03) which take speaker level from your aftermarket's HU and drop it to line-level to feed the inputs of another power amp. Sounds innocent, but all power amps add some distortion & noise to the output signal. This is because they switch large amounts of voltage & current thru power transistors, coils, and transformers which in turn overshoot, undershoot, hiss, and throw spikes into the output. Why add that into the signal you're going to feed your power amp esp. when your HU's manufacturer gave you 4-clean HV preamp outs to use?

To answer your question about whether the 8-speaker 4CH Toyota HU connector & harness has a wire going to the fuse: Yes it does, and GND too. I keep reading about people losing their radio & cigarette lighter lights. This may be a little late but...

(Warning: Never use the ground of any illumination lights to ground your HU or (anything else)! This includes the following lights: Cigarette Lighter, A/C Switch, Hazard Switch, a/t Shift Lever)

This is because their brightness is adjusted by varying their connection to ground by a dimmer circuit on the Combination Meter. If you fry it, you'll lose all those lights but your gauges will still work cuz they're on a separate dimmer circuit.

Don't know if it's a replaceable part, maybe someone can tell us this, otherwise you may have to get a new Combination Meter.

There's a dirty fix for this but I don't think this is the place to post it, maybe in a new thread if there's interest.

09-05-2003, 01:27 PM
has anyone found a cheap place to get this online?

10-01-2003, 12:33 PM
ur a smart dude for figuring that out, not learn how to host pics!

11-24-2003, 02:12 AM
The Scosche TA-03 Wiring Harness Kit is great if you want to do a clean install that's pre-wired to the right pins & right grounds, already has built-in attenuators for HV outs, is easy to hookup, & easy to remove. To keep it that way I stuck the 4 terminating resistors inside the TA-03 harness for the Mod. Later if you want, you can remove your HU in its original condition, disconnect the TA-03 and replace the stock radio, or connect the same TA-03 to a new HU and drop it in. Clean, simple.

But if you've already cut off the Toyota HU connector there's still hope. You can order a replacement R4 connector from your Toyota dealer (I've never ordered one so I'm not sure if comes with pins in it, if not I think they sell pins w/pigtails in small packs of 10 for repairs, see below). Or you might drop by a junkyard and cut the connector off of some GT-S or Lexus. For R4 Pinouts & Color Code see below.

Again this is a little long, but then it's for everybody else who's ever wanted to get rid of that noise but already hacked-off their Toyota HU connector, so here goes...

1) You'll need to find each audio line coming from your HU: FrtL, FrtR, RrL, RrR.

2) You'll need to find the ANALOG GROUND wire in the Toyota harness and free it up from any other ground wire it may be twisted together with.

3) You'll need to find the Output Impedance of your HU (specified in ohms).

4) You'll need 4 terminating resistors (1/8 watt to 1/2watt size) that match your output impedance, 20" of small hookup wire, some heatshrink tubing (or electrical tape), and some solder and a soldering iron.

5) You want to add some wire to the ends of the terminating resistors, so twist a short 4" wire onto the end of each resistor & solder it. Leave the other end of each resistor exposed for a 1/2" and slip some heatshrink over it and shrink it. Strip the end of the 4" wire and set it aside.

6) Find the centerwire of one of the 4 audio lines from the HU. Twist the centerwire onto the exposed end of one of the terminating resistors and solder it. Do this for all 4-lines. Go ahead and heatshrink or tape-up the exposed connections.

7) You should now have 4 short wires from the terminating resistors hanging loose. Twist all 4 wires together then connect them to the ANALOG GROUND wire you separated from the Toyota harness earlier.

8) Now take all 4 braided shield wires (from each audio line) twist them together, and connect them to the ANALOG GROUND wire too.

Which one's the ANALOG GROUND wire? It's been awhile since I had my dash apart so I'm trusting the manual which sez: SOLID BLACK (You'll know if you use the wrong one: it'll still be noisy)

Double-check your work, turn key to IGNITION, power-up your HU, listen for ECU noise, run your power-windows up/down, then start the Celi and listen for alternator whine. If you still get noise check you work again: make sure you're using the correct wire for ANALOG GROUND, make sure only the 4 short wires from the terminating resistors & the shields from the audio lines are connected to it, nothing else. --> don't connect the ANALOG GROUND wire to the car's ground, radio's ground lead, or radio's chassis <-- Connect the radio's ground lead to a ground bolt on the car.

If you don't have a soldering iron you can find inexpensive soldering irons at Radio Shack good enough to do the job, some RS's stock heatshrink.

Since each manufacturer designs their HU & Amp specifications differently (some have 2V, 4V, 5V, 8V PreampOuts with output impedances like 60ohm, 200ohm, 330ohm, 10Kohm, and 47kohm outs) matching them to the Toyota Premium Stereo Amp ideally means selecting the right values for the attenuating resistors (already in the stock TA-03 harness) and terminating resistors (added by the Mod).

Generally, the terminating resistors should match the output impedance of the HU, so that's easy. The only reason why you might want to add series antenuating resistors in each audio line (or replace the ones Scosche already put in their TA-03 harness) is if the sound gets too-loud & distorts when barely cranked up, or isn't not loud enough. Compare it to how loud your stock radio radio got. The stock amp won't go much beyond that, so your new HU should at least be able to match it if everything's right.

Wiring Harness Color Codes & Pinout for Toyota HU 20-pin R4 Connector:

1 BATT = BLU w/Yel Stripe*
7 Mute = Brown
8 FrtR = Red
9 FrtL = White
10 Shield (drain wire)
11 ACC = Gray*
12 FACTORY RADIO ONLY = WHT w/Grn Stripe* (Don't use! Cover w/tape!)
17 Beep = Green
18 RrR = Blue
19 RrL = Yel
20 GND (car chassis) = BROWN*

*1, 2, 3, 11, 12, & 20 (in caps) are individual wires, the rest are shielded together (pin 10)

(I think I got the pinouts right, lemme know if I screwed anything up)

'00-'02 Celica GT-S R4 connector: PN 90980-12038

Note: I'm not sure if these are the right pins for our R4 connector, but give your dealer the PN to point him in the right direction and maybe he can tell. Toyota calls them "Terminal, Repair":

Pack of 10 Prewired Female Pins w/6" Pigtails:
Terminal, Repair PN: 82998-12340

12-17-2003, 07:09 PM
Hey everybody,

Well, this is my first official post. I'd like to thank PacificBlue for the Mod. It works to about 95%.

I did everything like Blue said and the stereo works way better than it used to with that awful whine. However, the "whine" is still faintly there. I was wondering if anyone else still hears the faint whine and if so how (if possible) can I take care of it. My girlfriend can't hear it; but I can, I guess I am making a huge deal out of something so tiny. The slight whine is alternator whine, because when accelerating the pitch jumps. Like I said, it is so slight, it is almost not even worth bothering about but if there is an easy way to fix it, I'd like to know.

The stereo settings are perfect now. Without the mod I would play the volume on about 5 (out of 40) and the audio would be blasting. The resistors really helped tune down the sound. Now, I can jam at a comfortable 15-20.

Thanks Again PacificBlue and everyone else who has been posting car audio help,


12-18-2003, 02:10 PM
Sweet...I got everything fixed...COMPLETELY!!!

If you have your head unit completely pulled out of the dash and held far from the center console, there is absolutely no whine. The closer you move the unit, the louder the whine gets.

After doing the mod, the noise was dramatically reduced but not eliminated. What I did to rid myself of this final noise is mount the harness and the SC-4 box just behind the HU and above on the crossing piece of plastic.

No noise now.

12-20-2003, 05:54 PM
Okay so where do I get these termination resistors so I can get the ball rolling?

About to buy the Schoche TA03 & SLC-4.

12-22-2003, 02:29 AM
Nice feeling to be rid of that god awful noise isn't it?

Don't use the SLC-4 BlueBox Level Converter if you're going to connect your HU Preamp Line Outs directly to the Toyota Factory Amp, you don't need it - like I said, hang it on the wall and turn it into a dart board. The TA-03 wiring harness connector emulates the one on the back of the stock radio and mates directly with the connector in the Toyota GT-S harness. Use the SLC-4 only if your HU doesn't have PreOuts or LineOuts and you're forced to use the speaker outputs. The SLC-4 has transformers in it that unfortunately tend to pickup the electrical noise around it (that's why it's sensitive to careful placement behind the dash).

If you do the direct Mod without the SLC-4 BlueBox and crank your headunit up to max (during silence), all you should hear is some HU & amp hiss and very little else. There should be -zero- alternator whine, power window motor buzz, or ECU hash.

If you're in a hurry, you can try your local Radio Trash Store for resistors, or ask them where there's a decent electronic parts supply store. I used tiny 1/8 watt 5% tolerance carbon-film resistors so they'd fit neatly inside the heat shrink tubing and keep things tight. You can use 1/4 watt resistors which are a little bigger if you like. Here's a link to Radio Trash if you want to get 'em right away: 1/4 watt Carbon Film Resistors ( rs&fbn=Type%2F1%26%23047%3B4+Watt+Resistors). (8/07 updated link -PB)

"...dude, what'cher hearin' now is 1.21 gigawatts of silence"


12-22-2003, 08:53 AM
Okay, so as long as I don't use the SLC-4, & just use the TA03 I won't have any problems with noise from the alternator coming through my speakers?


Amer Q.

12-25-2003, 07:15 AM

1) Plug the 4 Male RCA's directly from the TA-03's harness into the HU's 4 Female RCA's. (Unless your HU only has SPKR Out's, in which case you'll have to use the BlueBox and mount it carefully behind the dash so it doesn't pickup noise, but also do #6 below).

2) Connect your HU's GND (-) wire to the 2 BLK (Digital & Chassis) GND wires in the TA-03 harness. Don't connect anything else to them.

3) Connect your HU's +12v wire to to the TA-03's own +12v wire. Don't connect anything else to this wire.

4) Make sure your HU's GND wire is not conected to something else's GND, sharing it. Only connect it only to the 2 BLK wires in the TA-03.

5) Check any crimp or butt connectors you may have added to any of the wires. Check for loose crimps making poor connections.

6) Run a separate GND wire from the HU's chassis (case) to a GND bolt on the Celica's frame. On many HU's you'll find a GND lug sticking out the back of the chassis for this. Don't rely on the tin mounting brackets to do your grounding for you, use real copper.

I ran a length of #16 guage heavy-duty flexible copper wire (GRN) bolted to the frame behind the Celica's dash to the back of my HU (hard to see in the pic, but follow alongside the green line drawn-in, or click on the link below the pic to view the ShockWave animatic). On one end I crimped a heavy-duty spade lug which slips under the Celica's top-left bracket bolt (see left arrow). On the other end I crimped a smaller eye lug and screwed it to the back of my HU. (You can see the HU's GND lug sticking out of the back in the pic (right arrow), but I didn't use it cuz i wanted it bolted-down instead)
Added: #16 guage heavy-duty flexible copper wire (GRN) from Celica's dash to back of HU.
[ Click here to view an SWF animatic following the GRN ground wire added in the pic ] [ Don't use the BlueBox! ] (

Note: I didn't want use this pic in the original post cuz it shows the Scosche BlueBox (which wasn't used in the final mod). Yes I hooked it up, yes I made-up 4 nice extra RCA cables to go between the HU and the box, and no it doesnt work very well in the Celica, so don't use it.

The only time the SLC-4 BlueBox should be used is if your HU only has SPKR LVL Out's (no PreOuts) and then you'll have to do the mod anyways because the transformers inside it will pickup noise inside the dash. You'll have to be careful about where you stick it and try to find a quiet place for it to live.

Anyway sorry, me bad for not mentioning this in the original post... without this chassis-to-frame ground wire you're almost sure to get some residual noise. I know cuz during testing I could hear the ECU buzz leaking thru until I cinched the bolt down tight.

I hope this solves any remaining noise problems for you.

(edited 12.30.05: add Red HL's)

12-28-2003, 09:40 PM
I haven't tried the ground yet, but everything is finally hooked up, subs, changer, etc.. i still need to remove the deck again to ground the body of the deck to the chasis.

another question for you is after your install, did you experienced any engine noise or turn on/power up "pop"? i have this turn on pop right not and i think it only on the stock speakers.
please let me know.

12-29-2003, 04:30 AM
No noise, but I get a "pop" if the ignition's already ON and I turn the HU OFF manually, but I never hear it cuz I always leave the HU on and turn everything on/off with the ignition key: When I put the key in and start the car, everything turns on and comes up smoothly. When I turn the key OFF, same thing... everything shuts down smoothly, no pop - ever.

I forgot all about the HU PowerOFF pop until your post and had to run out to the Celi to check it out. Right after I did the mod I remember trying to figure out what was causing the pop whenever I turned the HU off but not the key. I never took the time to look into it, then forgot all about it cuz I always leave it ON.

The two common causes of PowerON/PowerOFF "pops" are:

1) HU's preamp outputs have DC transients on them during power-up or shutdown.

2) Power amp's outputs have DC transients on them during power-up.

Most head units have an AMP CONTROL wire which connects to the Remote Input on the external amp to turn it on/off by the power button on the HU (including the stock radio). But how elegantly they control the remote PowerON/PowerOFF timing of the external amp may be different from manufacturer to manufacturer (like from nil to maybe a one-second delay). Interesting thing is, the stock radio never popped no matter what.

Some external power amps have built-in muting relays to keep the speakers from getting connected to the output stage until the amps have stabilized (ever hear that delayed "click" coming from the inside of a high-end high-power amp, EQ, or crossover?)

Head unit PowerOFF pops are harder to fix than PowerON pops. If you turn your HU OFF and its preamp outputs have transients on them during the shutdown and the external amp is still ON, there'll be a pop in the speakers. But how do you turn OFF the external amp before the HU if the OFF button you're pushing is on the HU? Ideally the remote AMP CONTROL wire should turn OFF first, then the HU should turn itself OFF a second later.

PowerON pops are easier to fix because you can connect a delay relay between the AMP CONTROL wire and the Amp to turn it on a second later after the HU's preamps have stabilized. If you've got a PowerON pop you can try a STINGER "SGN21" which supersedes their older "SPSON" module to see if it fixes the problem:
"SGN21: Stinger PopStopper"

12-31-2003, 11:10 AM
This thread is exactly what I have been looking for, but I was hoping someone might be able to answer a few questions.

I just ordered a Sony CDX-MP80, it should be here soon and I wan't to install it asap. After reading this post I also ordered the Scosche TA-03 adapter kit from sound domain. From what I understand, I DO NOT need the SLC-4 blue box because I have rca pre-amp outputs. All I need to do is the noise reduction mod to the TA-03, right? Now I am not sure on what kind of resistors I need to purchase for my head unit. I was hoping someone here could help me figure this out.

Here is detailed info on the Head Unit
I am having a hard time finding out the ohms on the deck, all I can find is 2 4volt preamp outs with high pass and 1 4volt sub out with low pass. So what kind of resistors do I need? Do I need to modify the resistors already inside the TA-03 or can I leave them? Any help would be greatly appreciated. thanks in advance.

12-31-2003, 05:45 PM
This post goes out to dchan8 & Tryan77 who've been brave enough to try this mod and to keep me on toes searching for the math to resolve the termination value question. Reverse-engineering is like hacking, you don't give up until you've got it all figured out and then you're a little smarter and grin a whole lot:

I knew the series resistors that Scosche put in the RCA cables of the TA-03 were part of an "L"-pad attenuator network, used to drop higher-level audio to lower-level audio. But what was their intended design spec? My best guess was that it was originally meant to be a 50% voltage divider into a 2k input load for some Toyota factory amp (500mv in = 250mv out, etc), but not ours.

Our factory amp has practically no input termination, so it puts no load on the TA-03 & HU and the series resistors basically don't do anything except pass pretty much the full voltage from the HU to the amp (which in turn makes it sound too loud & the volume dial way too sensitive).

I searched the internet looking for some old audio equations I knew were out there and yep, it's true - the Truth is out there somewhere... I'll give you a range of resistor values first, then leave you with a couple of links if you want to learn more about this sort of stuff:

8v : 36 ohms = 150mv / 48 ohms = 200mv

5v : 60 ohms = 150mv / 79 ohms = 200mv

4v : 74 ohms = 150mv / 100 ohms = 200mv

2v : 154 ohms = 150mv / 211 ohms = 200mv

(this table is updated in a later post: Final test Results (

Assuming the factory amp wants to see 150-200mv of signal at its inputs w/termination, and using the existing series resistors in the TA-03 harness, these values should work.

In my setup I used 60ohms so the factory amp is theoretically getting 150mv. It sounds & works great, but I'd probably try using a higher value resistor next time to get me closer to 200mv so I'd have more volume range to crank up the quieter tunes.

Don't forget, these numbers are based on using the existing series resistors Scosche put in the harness. If you want to build a "by-the-book" perfect "L"-pad, you may have to replace them with other values. Here's a couple links explaining attenutation and voltage-dividers:

"Line level signal to microphone input adapter" (

"The Voltage Divider Rule" - Resistive Dividers (

"Voltage Divider Calculator" (

If you want to follow dchan8 & Tryan77's troubleshooting thread click here:
"Termination Resistor" - dchan8 & Tryan77 (for Alpine 10k 4volt PreOuts) (

12-31-2003, 06:35 PM
does this mean that i should try for my alpine(4v preouts) a resistor from 74-100 ohms?

12-31-2003, 06:55 PM

In audio, 10k impedance is still considered a "high-impedance" and prone to picking up some noise unless well-shielded.

I'd try the 100 ohm, it should kill any remaining stray noises you've been tackling, give you plenty volume, and leave your volume control set so you don't have to max it out to hear the softer tunes.

01-01-2004, 11:09 AM
sorry to be a nag but,

So if my pre-amps are pumping out 4 volts, then you suggest doing this mod using 100 ohm resistors?

This is my virgin electronics experience and I don't want to mess anything up when my HU gets here next week.

01-01-2004, 07:39 PM
lowendfrequency - Yep it looks that way so far, least on paper. We're waiting for dchan8 & Tryan77 to finish tuning their Alpine 4volt HU installs to find out if the math works.

It's kinda difficult trying to figure this out by "remote" cuz I'm not there in front of your rides where I can help you test & tune them. That's why in the TA-03 Noise Mod post I said the 60 ohm terminators's worked for my HU, but the values might be different for yours (if it's got different output voltages & impedances than mine).

According to the math there are many ways to accomplish the same goal (match levels, impedance, signal transfer, minimize or eliminate noise). But which one to use depends on the gear's specs, type of power source, grounds, electrical envoironment (noise), shielding, etc.

For us, with our super high-tech, muchly-electronic, almost fly-by-wire 7th Gen Celica's, there are computers communicating with & controlling everything everywhere, talking over wire harnesses that rival ones used in 747's, we share power to everything off of one poor little 12 volt battery, we share the same ground which floats on rubber insulators (tires) that keep us from using a "real" ground (mother earth), we generate high-voltage sparks to startup our HID's, more sparks to fire-off the sparkplugs that make us go & give us Lift, we generate mega-pulses of power to recharge our battery (alternator), and we generate more noise everytime we switch-on or roll a window, sunroof, or cabin air blower, and we expect our super-sensitive high-end audio gear to be noise-free in all this soup?

Yep. So, based on collecting the 411 from mod'ing mine & others trying to mod their's, then applying the formulas used for calculating the resistors for building an "L"-pad attenuator (with a little rule-bending), it looks like the resistor values in the last post (above) will probably work ok in this hostile environment. Just find your HU's PreampOut voltage in the left column and pick a resistor value between the two values listed in the chart.

You're right about the Sony CDX-MP80 output impedance specs being difficult to find. But that's okay, the math has already been done for you and the termination resistor values in the last post should work fine for the PreampOut voltages shown. So if your CDX-MP80 has 4volt PreampOuts, you'd use a 100 ohm termination resistor on each audio pin on the TA-03 harness connector just like the 4volt Alpines.

But, you might wanna hang out for the results from dchan8 & Tryan77 first, or go ahead and be real brave and join their "Alpha test" team. The more 411 we get the better and the sooner we'll know what works best.

01-02-2004, 07:06 AM
Thanks for getting back to me man,

I should be getting my HU on monday, and the TA-03 sometime soon after, so I'll hold off till then. After that I think I will become an alpha tester as well.... gonna pick up some 100ohm resistors today and go over everything to make sure I know what I'm doing.

So, just to make me feel better, humor me real quick. Worst case scenario....The noise mod doesn't work, I get loads of alternator whine and electrical buzz, and am forced to bypass the factory amp to get rid of it, right?

01-02-2004, 08:17 AM
Don't worry there's no question the mod works, you just have to pick the right value termination resistors for your particular HU and you're done.

Personally, I tried the TA-03 just to see if I'd be happy with a new HU powering the existing amp & speakers. Answer? I'm very pleased. Plus, I always knew I could install an aftermarket setup later if I wanted to. In fact I went ahead and added a sub because the Celica's sound system really lacks bass (it doesn't have a trunk or airtight enclosed compartment that can support a decent low-end bass setup). Now, it kicks ass.

How much sub, bass, midrange, highs and SPL (sound pressure level) you want is a personal choice. Take a look at the "Pics of trunk setups here!" ( thread and you'll see what I mean.

You can always bypass the factory amp if you want to, but it's a little bit more work than mod'ing the harness. You'll have to locate a place to mount your new amp, disconnect the old one, patch into the wiring harness for power, IGN, and GND, and splice into existing speaker wires. You'll find instructions on this board and others complete with color codes.

Try your new HU with the TA-03 & Noise Mod for now. You can always add aftermarket gear later if you want to.

01-02-2004, 11:48 AM
i just tried the 100ohm resistor, and there is pretty much no ecu or engine noise, but i have to max my volume to get it to be pretty loud(kind of normal for me) but it's not loud enough, what size should i try next?

01-02-2004, 02:20 PM
Originally posted by dchan8
i just tried the 100ohm resistor, and there is pretty much no ecu or engine noise, but i have to max my volume to get it to be pretty loud(kind of normal for me) but it's not loud enough, what size should i try next?

Are you running 4volt preamps? I just purchased some 100 ohm resistors to do this mod but it sounds like I might have to take them back. How loud is it compared to what it was stock? I usually listen at a medium level but I like to crank it now and then and I don't want to lose any power.

Also, what should the wattage be on these resistors. I bought the ones that looked most similar to the ones in the pictures that pacific blue posted, they are QW110 100ohm 1/4Watt Flameproof resistors w/ metal film. Does that sounds right?

01-02-2004, 03:36 PM
according to pacificblue,
1/4 to 1/2 watt is fine for the resistors.
i have 4v preouts too. i suggest to use 470ohm resistors. i think this is the boundary for engine nose and not. keep in mind that you probably won't be able to hear any engine noise when the car is running and you have some volume with the stereo.

01-06-2004, 01:02 PM
got this mod workin in my car with 300ohm resistors, works like a charm :thumup: A+ work here pacificblue

01-07-2004, 06:42 AM
Wow!, looks like everyone finished tuning their mods... Excellent! This is my first chance to catch-up with the board since returning to work after vacation. You guys just made my day.

So it looks like feeding the factory amp about 500mv signal is the magic number. Here's a list of the termination resistor values each of us ended up using w/comments about the results:

150mv / 5v 60 ohms "It's plenty loud but the dial is spread out, so I may try it with 211 ohms later so I don't have to max it just to hear the softer tunes." - PacificBlue

432mv / 4v 230 ohms "If I changed anything I would try a "slightly" lower resistor. I think something between my 230 and the next lower size of 150 might eliminate virtually all the noise and still give people similar to me, enough volume." - Tryan77

546mv / 4v 300 ohms "The 300ohm resistor was the perfect match for me, I can't even detect a hint of ecu/alternator noise but I can still crank it as loud as I dare and have room left to go." - lowendfrequency

793mv / 4v 470 ohms "i settled on 470... this has a little/faint ecu noise when the car was off, but on start. no ecu noise when the key was in the on/acc position" - dchan8

So 333.3 ohms was the average of the three Alpine 4v setups.

Here's the updated termination resistor selection table. Don't forget, these numbers are based on using the existing series resistors Scosche put in the harness:

(update 7/07: Instructions for Calculating Values for newer TA-03B harness)
Note: The TA-03A harness uses 1900 ohm series resistors while the newer TA-03B uses 2200 ohm resistors, so if you're using the newer TA-03B and want to be precise, add +16% to the value found in the table below for your termination resistors, or follow the instructions on how to use the Voltage Divider Calculator linked further below. Resistors are usually rated with a +/-10% tolerance, so it's really no big deal if you want to stick with the table.

(update 8/07: Termination Resistor Values for HU's with only 2-RCA Outs)
Note: If your HU only has two RCA outs (L&R) you can use an RCA Y-Cable to connect to the StockAmp's Rear RCA's, but you'll need to roughly double the value of the termination resistors to avoid double-terminating the signals and losing level. For example if the table says use 600 ohms, use 1000-1200 ohms instead.

Just find your Preamp-Out Voltage on the left, then use the resistor value shown in BOLD for your mod.

8v: 36 ohms =150mv / 48 ohms =200mv / 61 ohms =250mv / 126 ohms =500mv / 271 ohms =1volt

5v: 60 ohms =150mv / 79 ohms =200mv / 100 ohms =250mv / 211 ohms =500mv / 475 ohms =1volt

4v: 74 ohms =150mv / 100 ohms =200mv / 127 ohms =250mv / 271 ohms =500mv / 634ohm =1volt

2v: 154 ohms =150mv / 211 ohms =200mv / 271 ohms =250mv / 633 ohms =500mv / 1.9k =1volt

1.8v: 173 ohms =150mv / 237 ohms =200mv / 306 ohms =250mv / 731 ohms =500mv / 2.4k =1volt

The resistor values in BOLD to produce 500mv are highly-recommended, the values for producing 1volt out are for reference only and definitely not recommended. If you want to put more spread on the volume dial use a lower value resistor, if you want more guts on the dial use a higher one.

If you want to build a "by-the-book" perfect "L"-pad, you can do the math and replace the series-attenuator resistors Scosche built into the TA-03 harness and the mod's termination resistors with custom values. Here's a couple links explaining attenuation and voltage-dividers:

"Line level signal to microphone input adapter" (

"The Voltage Divider Rule" - Resistive Dividers (

"Voltage Divider Calculator #2" {added 12/30/06 to replace dead link} (
(update 7/07: Instructions for Calculating Values for newer TA-03B harness)
Note: Input R1=1900 for TA-03. Input R1=2200 for the TA-03B to get the correct termination resistor value.

If you want to follow dchan8 & Tryan77's troubleshooting thread click here:
"Termination Resistor" - dchan8 & Tryan77 (for Alpine 10k 4volt PreOuts) (

And here's a review & summary of all the 411 we gathered from reverse-engineering, mod'ing, testing, and tuning:

High-end aftermarket head-units equipped with high-voltage (2v, 4v, 5v, 8v) preamp outputs place the audio signals way above the noise found in our cars, but are too hot to directly drive the factory amp used in the 2000-2002 GT-S w/Premium 8-Speaker Stereo system without sounding too loud in the midrange and picking up all sorts of electrical noises from the car.

Because the stock amp has a very high input sensitivity, the aftermarket HU's PreOuts need to be attenuated from 2v, 4v, 5v, or 8v to approx. 500mv (.500v) in order to drive it to full output without distortion. Also, because the amp has a very high input impedance of 1-meg or higher, it needs to be properly terminated in order to drain the electrical noise picked up by the audio lines to ground before they reach the amp. Among the potential sources of noise in the Celica are its multiple ECU's, cabin light dimmer, power windows, power sunroof, power doorlocks, front & rear windshield wipers, HID's, ignition system, alternator, and any aftermarket gear like neons, inverters, guages, etc.

Using the inexpensive Scosche TA-03 wiring harness you can connect an aftermarket HU with the Celica GT-S' wiring harness without cutting the connector off or splicing wires, but it must first be modified with the addition of 4 termination resistors to accomplish two things: 1) to attenuate the HU's signal level down to 500mv's and 2) to terminate the audio lines between the HU and factory amp so that any noise they pick up will be drained to ground thru the resistors before entering the amp. By adding the 4 termination resistors in a bridging configuration and using the existing series attenuating resistors already built into the TA-03 harness, we form an "L"-pad attenuator which reduces the level and drains the noise at the same time. The factory amp can then be driven to full output without loss of low-end (over-bearing midrange), distortion at high levels, or picking up surrounding electrical noise.

btw: If you don't feel comfortable doing an audio install by yourself after studying these boards, I highly recommend you find a professional installer in your area by posting a question in the Audio & Electrical Forum and asking for one; some are better & more familiar with the Celica than others and this is probably one of the best ways to find one. You could also ask if any member in your area would be interested in helping you or doing it for you, can't hurt.

Thanks again to everyone who posted their questions, comments, suggestions, & results. Like I said, I'm real pleased with how the Celica sounds now with the stock amp & speakers w/new head-unit & sub, and even more pleased to be rid of that god-awful noise.

Now the rest of you Celi lovers out there that have been dyin' to stick a better head-unit in the dash and were worried about how to do it, can do it.

"Bill?" "What is it Ted?

"...the next sound you hear will be 1.21 gigawatts of most excellent ( silence!"

03-29-2004, 04:46 PM
So if I have a preout out impedance = 2.2v/1k Ohms (I think)

here is a link to my manual

what type of teminating resitors do I need give the results for a 2.2v
154 ohms = 150mv / 211 ohms = 200mv / 271 ohms = 250mv / 633 = 500mv


03-30-2004, 01:39 AM
Because the stock amp has a very high input sensitivity, the aftermarket HU's PreOuts need to be attenuated from 2v, 4v, 5v, or 8v to approx. 500mv (.500v) in order to drive it to full output without distortion.

...according to the chart 633 ohms is what you'd use, but since that's not a standard off-the-shelf value buy the next closest value: 620 ohms.

04-12-2004, 08:18 PM
i have this HU

so which resistors should i get?


04-12-2004, 09:53 PM
Looks like the Pioneer DEH-P750MP CD WMA MP3 Player has 6 volt PreOuts. So 172 ohms would give you 500mv, but again that's not a common off-the-shelf value so use 150 ohms (or 180 ohms) instead.

04-13-2004, 07:30 PM
thanks pacific,
i have a few more ?'s though
what do you mean by "unsoldering" at the beginning steps of this mod? i'll be buying a soldering gun this weekend, never actually used one...
right now, i'm planning to install this unit temporarily until i get my jdm console would it be alright if i just leave the resistors which were for the pioneer, and just plug and play with the alpine, or do i have to get new resistors?
also, the last step requires a ground from the hu chassis to the celica frame, is this really necessary? i don't really know where or how to do this part


04-13-2004, 09:21 PM
The 2-RED and 2-YEL wires in the pics are the center wires of the RCA audio cables in the Scosche TA-03 Harness. Scosche slips a short piece of black heat shrink over them, solders 'em to the Toyota connector, then slides the shrink tubing over the solder joint & pins and heats them to shrink tight so nothing can short out across any exposed pins.

I used an exacto knife to slit & remove the black heatshrink so I could expose the wires and unsolder them from the pins (hold the soldering iron on the pin until the solder melts so you can pull the wire free).

Once the wires are free it's easy to twist the resistors onto the exposed ends. After that, "tin" the ends by touching the soldering iron to each end and apply a tiny bit of solder until it flows into the wires, then immediately pull the soldering iron away so you don't melt the RED or YEL jacket. After the ends are cool slip a short piece of heatshrink over them.

If you tinned the ends enough you should be able to rest each wire on a pin, press the soldering iron on top of the wire and it should melt the solder and flow onto the pin. Lift the iron as soon as the solder melts. Hold the wire still - don't move it or else you'll make a cold solder joint which is mechanically weak and electrically "iffy". If it looks shiny, it's good. If it looks matte finish it can't be trusted, reheat & try it again.

After the pins cool, slide the heatshrink over each pin and heat with a heatgun or hair dryer until it shrinks. Don't overheat 'em or they may burn & curl.

The Alpine IVA-C800 has 4volt PreAmp Outs and would ideally need 271 ohm resistors in the harness, but you probably won't notice too much of a difference. You'll still be able to crank it up and it'll still be loud, but you may have to turn up the dial more than your Pioneer. I'd mod the harness for the Pioneer and not worry about the Alpine levels.

In answer to your question about the extra GND... I installed it while troubleshooting the original TA-03 noise problem. After figuiring it out I began wondering if the extra heavy-duty ground was still really necessary. With the key turned to accessory, engine OFF, and HU ON, I could hear a faint tiny bit of noise from the ECU. When I connected the heavy-duty GND wire to the Celi's frame and cinched the bolt down - the noise disappeared.

If you use metal brackets bolted to the sides of your HU, then bolt the brackets to the Celi's frame, this should take care of all the grounding you need, but the best of the best will tell you that it never hurts to run an external heavy-duty GND Strap or GND Wire because "brackets & bolts" have a tendency to work themselves loose over time thru vibration.

I hope this helps.

04-14-2004, 06:53 AM
that really helped alot, thanks
i will try and do this mod this weekend

thanks again

05-06-2004, 11:40 AM
I just got fed up and rewired the pre-amp. No Noise. Took 15 minutes start to finish :-)

05-12-2004, 08:00 PM
Thanks PacificBlue for the install info and everyone for their ohmage (is that a word) feedback.

I used the 620 ohm and it sounds pretty close to when I had it in my other car. I do hear the pop when turning it off but that is something I generally never do.

Thanks again all rocks!

01-09-2005, 08:41 PM
this thread rocks
i havent even messed with my radio yet but this is what i have gathered from this thread and all the links that deal with it
this only deals with the premuim sound in the gt-s
i take it the jbl factory sound thats in my 03 gts is premuim

the head deck i have to put in is my alpine 9813

this has 3 sets of pre outs
front rear and sub
these are 4 volt pre outs
( so i would be shooting for 271 ohms@500mv?)
found here 270ohms 1/2 w resistor

am i forgetting some thing besides the long deck to chassis ground?
oh and where can i get a din mount w/ the little pocket underneath?

thanks in advance

01-10-2005, 10:32 PM
I'm glad the thread is still helping out. It was written for 2k-2k2 Celi GTS owners with the 8-Speaker Premium Sound System (not for GT's). Scosche still specs the TA-03 for 2k & up Celica's, so it should work on your 2k3.

Yes, 270 ohms is the magic number for your Alpine. Keep in mind resistors get physically bigger the higher the wattage rating, so although you can use anything from 1/8 watt thru 1/2 watt at 270 ohms, I'd try to stick with 1/8 or 1/4 watt resistors as they fit inside the shrink much better.

As far as the single DIN mounting kit w/pocket goes, probably the most popular one is the SCOSCHE TA2045 with small pocket underneath. You can check it out here: Scosche TA2045 Single DIN w/Pocket (

Larry Dougherty did an awesome job custom mounting his HU in a Single DIN mounting kit available from the UK. have a look here: Single DIN mounting kit (

It can sometimes be a little difficult holding two heavy pieces of HU gear stable in a double DIN mount, but when Chiznarles still had his 2k Celi, he installed a Double DIN mounting kit and finished it off with a pair of Toyota OEM side fillers to make it look nice and smooth. You can check that out here: Double DIN Installation Kit (

The heavy-duty ground is something I did cuz I just don't like depending on the mounting brackets for grounds, especially if they're going to conduct power to ground and double as a pathway for noise to ground. I'd rather trust a nice hunk of copper wire anyday over Japanesium brackets that were never designed to serve as grounds in the first place.

Have fun doing the mod and enjoy the Alpine!

01-12-2005, 06:17 AM
Originally posted by PacificBlue
It was written for 2k-2k2 Celi GTS owners with the 8-Speaker Premium Sound System (not for GT's).

Well I guess i'm one of the few GT owners that has a premium sound system and has benefited from your posts.

Has anyone tried the BHA8113 from best kits and harnesses a.k.a. stinger-aamp. I spoke with them and their harness uses 2k ohm resistors on the rca leads.

01-12-2005, 07:48 AM
Yes you are...

According to the 2000 brochure the GT comes standard with: "Deluxe 3-in-1 AM/FM ETR/Cassette/CD with 6 speakers". But you could order the "Upgrade Package" (Upgrade Package - includes power windows and door locks, and cruise control) and then add the "Premium 3-in-1 AM/FM ETR/Cassette/CD with 8 speakers" to the order.

According to the Toyota Schematics, the standard "Deluxe" system (without separate amplifier) uses a 10-pin R2 & 6-pin R3 connector (Scosche TA-02 harness works here), and the "Premium" system (w/separate amplifier) uses a 20-pin R4 connector (Scosche TA-03 harness w/mod works here).

I'll update the top of the thread later when I have more time, thanks for the 411. (01/12/05: done -pb)

The BHA8113 from in the pic below looks identical to the TA-03, and 1.9k/2.0k is essentially the same value (within 10% tolerance). I didn't want to slit the heatshrink open on my TA-03 to find out, so I measured the them with an ohmeter and each one read about 1.9k. So like I said, the BHA8113 kit is probably the same harness as the TA-03 kit. You can compare them for yourself: BHA8113 - "20 Pin Premium Toyota Harness w/RCA"
(If anyone actually tries the BHA8113, PM me or post here to share your results) - TA-03 "2000-Up Toyota Amplifier Harness"

Reminder to those "speed-reading" this thread, yes these harnesses will work, but you've gotta mod them first. So don't go ordering one and think it'll work straight out of the package.

01-13-2005, 11:49 PM
Update 01/13/05:

I got tired of Imagestation & Tripod leaving commercial pic-ad breadcrumbs behind trying to coerce non-members to join, so I switched imagehosts to ImageShack(TM).

Let me know if there are any problems viewing pics, just PM me instead of posting here (the thread is already long enuff).

~ thanks.

Update 01/14/05:

Added 1.8 volt calculations for newer Clarion HU's:

Click Here: For a table of Termination Resistor Values and Final Test Results (

01-14-2005, 11:08 PM

I moded the BH8113 harness with 220 ohm resistors with great success. This harness has 2k ohm resistors so I had to take that into consideration. The 2k resistors were verified with a voltmeter.

Your average calculation of 333 was my goal. Using the 220 was about 13 ohms lower than your average. I have alpine CDA9827 with 4v outs. There were no signs of alternator or electrical noise.

If I were to have purchased the Scosche TA03 I would have tried the 330 ohm resistors which would have put me 3 ohms lower than your average.

Thanks for the help

03-19-2005, 04:21 PM
I have created an install guide based on this post in hopes that it will be better accessable to all those looking for help. Also, so it wown't be sitting at the top of the audio forum forever. ;)

The install guide should appear in the audio install guide section soon.

03-20-2005, 06:12 AM
Does anyone have a Scosche TA-03 for sale

12-22-2005, 10:49 AM
hey pacific, can you tell me what kind of resistors I'm going to need for the Alpine CDA-9851, im geting it pretty soon and am hoping you can tell me what kind ill need so the install can go smoothly for me. Thanx

12-22-2005, 11:13 AM
Your Alpine CDA-9851 has 2volt PreOuts, so according to the chart below you'd use 633 ohm resistors. Since 633's aren't standard off-the-shelf values, you can buy 620 or 680 ohm resistors.

Click Here: For a table of Termination Resistor Values and Final Test Results (
{don't touch the scrollbar - let the page load}

12-22-2005, 02:33 PM
thanx pacific, ill let ya know how it works out with those.....

12-26-2005, 10:13 AM
Ok I have a couple questions. I am installing a sony cdx-f7710 in my girls gt-s and I can not find the preamp output voltage in the specs. However on the box I see a small square that says "3pre4v". I am assuming this means it has 3 preamps at 4v. Would this be a correct assumption? So would that mean I need to get a ta-03 and I would need a 271ohm resister (or the closest to that obviously) to make it work in her car? I am just changing the headunit and running the factory everything else. I just want to make sure I am getting this right. Thanks

12-26-2005, 11:47 AM
Your Sony CDX-F7710 has 2 + 1 sets of preamp outs:

4-Volt Front & Rear Preamp Outputs with Selectable High-Pass Filters
4-Volt Subwoofer Preamp Output with Selectable Low-Pass Filter

So yes 271 ohms: or an off-the-shelf value would be 270 ohms.

(and of course, since the FactoryAmp doesn't support a discrete sub, your Sub PreOut doesn't get used unless you add your own)

12-26-2005, 11:54 AM
Your Sony CDX-F7710 has 2 + 1 sets of preamp outs:

4-Volt Front & Rear Preamp Outputs with Selectable High-Pass Filters
4-Volt Subwoofer Preamp Output with Selectable Low-Pass Filter

So yes 271 ohms: or an off-the-shelf value would be 270 ohms.

(and of course, since the FactoryAmp doesn't support a discrete sub, your Sub PreOut doesn't get used unless you add your own)

Thanks alot. I know she is dying to get it in the car so I will go pick them up this week. Thanks alot.

12-29-2005, 10:40 AM
The Resistor mod worked very well. The install went very smoothly, thanks to a good soldering iron. I almost get no feedback at all, except for a tiny alternator whine is noticable when the music is paused, but who the hell pauses it anyway. Also, the Euro single DIN looks fantastic, and I suggest it to everyone.

12-30-2005, 03:10 PM
couple more questions.... where does the digital ground go? also in the back of the factory head unit it looks like there are two antenna inputs I am assuming i just use the bigger one for my radio correct? the other just doesnt get connected? and the connector on my new headunit has a chassis ground wire as well. do I connect that to the chassis ground wire on the ta-03? or just connect both those to the chassis?

12-30-2005, 07:05 PM
"couple more questions.... where does the digital ground go?"
(...or come from?) It came from the StockRadio and went nowhere. Huh? See further below: *Toyota R4 Connector)

In modern mixed-circuit design, design engineers try to keep audio, video, computer, & power circuits isolated as much as possible. Each has its own ground path. Capacitors, baluns, inductors, and sometimes active electronics are used to filter & drain the different kinds of noise as much as possible. It isn't until just before these signals leave "the box" (in this case your HU) that the multiple grounds may get tied back together again.

Still, some signals that are especially prone to getting invaded by noise when outside the box (like audio) have their grounds intentionally kept separate from chassis ground even when leaving the box. Such is the way with most modern HU's: Your HU's RCA grounds come direct from the Output Preamps. Manufacturers expect you to connect them directly to the RCA's of your aftermarket PowerAmp using RCA extension cables.

Nothing should tap into these lines' grounds on their way to the Amp. They should be dressed in the trough on one side of the car by themselves, while power, control wires, remote changer wires, etc. should be carried in the opposite trough.

Since Microprocessor Noise is probably the worst offender second only to Alternator Whine, your HU's microprocessor ground gets tied to its Case (chassis) Ground just before leaving the box (aka: the BLK wire). Manufacturers expect you to connect this wire to one of the car's "real" ground points (Toyota lists Ground Points in all its Service Manuals).

*In the Toyota R4 connector (which the TA-03 plugs into) there are actually 3-different grounds:

PIN-10 SGD3 (aka: DIGITAL GND, Radio-to-PowerAmp Wire Harness Shield, & is only connected to Radio side)
PIN-16 SGND (aka: ANALOG GND, RCA Signal Ground)
PIN-20 GND (aka: CHASSIS GND, goes to a real Ground Point)

PIN-10 & PIN-20 get tied together in the Scosche TA-03 harness because your HU only has one BLK GND wire.** The stock radio had separate grounds within the radio for CHASSIS GND vrs. WIRE HARNESS SHIELD GND.

**The Toyota WIRING HARNESS has a pair of ECU lines carrying Tx/Rx DATA to the StockRadio which is "NOISE" to the audio circuits, so Toyota/Fujitsu provided a separate SHIELD in the WIRING HARNESS and a pin to dump it to called "SGD3" aka: PIN-10 DATA GND. YOUR new HU doesn't have Tx/Rx DATA lines which connect to the Toyota Harness, so PIN-10 has nowhere to dump to - but because the WIRING HARNESS still carries Tx/Rx DATA from the ECU, it's important to get this SHIELD connected to ground and the best place to do this at the HU is by tying PIN-10 to PIN-20. And -because- it has some residual ECU noise in it, you -don't- want to connect this to PIN-16 RCA Signal Ground.

To make sure you ground everything right, go back a page in the thread and do the checklist, if you leave the scrollbar alone this link will take you right to the post...
Click Here: Troubleshooting Grounds (

"...also in the back of the factory head unit it looks like there are two antenna inputs I am assuming i just use the bigger one for my radio correct? the other just doesnt get connected?"
I think what you're calling the "larger one" is the HU's FM antenna, and its smaller sister is the AM antenna.

"...and the connector on my new headunit has a chassis ground wire as well. do I connect that to the chassis ground wire on the ta-03? or just connect both those to the chassis?"
Same place as "Troubleshooting Grounds" above.

12-30-2005, 08:26 PM
thanks again. I went ahead and tied the chassis ground and digital ground together and attached them to the chassis and have no problems. Also I did the resister mod and have 0 feedback noise. only thing I hear is when you turn the radio off it thumps a little but that seems to be common. Other than that she is very happy and I am glad I'm finished with it. now I can get back to working on my car. Thanks alot for your help.

12-30-2005, 08:27 PM
oh and whoever mods this section should definately sticky this post. It is extremely helpful.

01-24-2006, 06:36 AM
I was really glad to find this thread. The noise problems I've been having (subtle alternator whine and some relay pop from the brakes; too loud at low volumes) are described here pretty accurately. I am using the TA-03 with an Alpine CDA-9851.

The only wrinke is, I'm not driving a Celica. I have a 2000 Avalon with the "premium" factory sound system. Does anyone happen to know if that amp has the same problem? I am somewhat familiar with electronics but I am no electrical engineer (I am a software guy), so I don't really know how to determine the answer on my own. I am hesitant to attempt this mod without knowing for sure whether it will fix my problem.

Thanks in advance for your replies!

TRD S'Charger
02-06-2006, 05:53 PM
can't you use the ta-03 without modding it if you are going to bypass the amp and just use the headunits speaker wire?

i mean wouldn't that save from cutting into the factory wiring of the headunit.

02-07-2006, 07:57 AM
can't you use the ta-03 without modding it if you are going to bypass the amp and just use the headunits speaker wire?In which case you would use a different harness altogether, not the TA-03.

TRD S'Charger
02-09-2006, 06:09 AM
um, which one then, according to crutchfield their aren't any?

02-09-2006, 08:03 AM
You have an '01 GT... unless you have the optional 8 spkr system.. you don't have an amp & would use the Scosche TA-02 or equiv. If you have the 8 spkr system or a GT-S... & wanted to bypass the factory amp - you could use that same harness for power, dimmer, & power antenna... but the spkr outs wouldn't use the harness but would be spliced directly to the speaker connections which you cut away from the external amp to bypass it or you would run separate wiring right to the speakers.

I, also, stand corrected... if you had the 8 spkr system you could use the TA-03... but you wouldn't be using the pre-amp outs... you'd be doing the same as you would if you used the TA-02. But, why pay the additional price for the TA-03 if your bypassing the factory amp?

See also:

TRD S'Charger
02-10-2006, 05:09 PM
i get it now, yeah i ordered my car with the 8 speaker system. i went to crutchfield and selected 6 speaker system and i get the wiring harness. thanks for your help.

R K e 1 C A
05-18-2006, 09:53 PM
could someone let me know what resistor is needed

<---audio newbie

the Headunit is a Clarion ADX5655z

BTW...can this mod be completed w/out soldering?...i'm still in CA and all soldering tools are @ home


05-19-2006, 03:02 AM
I think your HU is 1.8v out, so you'd wanna use as close to 731 ohms as possible to get 500mv out, up to 1K (1000 ohms) which you can find at almost any Radio Shack. This is from the mod chart higher above in the thread:

1.8v : 173 ohms = 150mv / 237 ohms = 200mv / 306 ohms = 250mv / 731 ohms = 500mv / 2.4k = 1volt

Can you do the TA-03 mod w/o soldering? I dunno, never crossed my mind cuz soldering seemed so much easier & more reliable to me. But you'll never know until you try.

R K e 1 C A
05-19-2006, 10:01 AM
Thanks…finally found a place that listed the preamp outputs

You’re right about the 1.8:


2 sets of 1.8-volt preamp outputs
wireless remote
16 watts RMS/45 peak x 4 channels
Zero-Bit Detector Mute circuitry
CD frequency response 10-20,000 Hz
CD signal-to-noise ratio 100 dB
tape frequency response 30-20,000 Hz
tape signal-to-noise ratio 67 dB
FM sensitivity 11 dBf
1-year warranty

so then this is what I’m still looking for:

731 ohms = 500mv

06-15-2006, 12:41 PM
Hi guys, I just got a Kenwood DPX-701 it has 5 volt RCA's and I tried Installing it with the Scosche TA-03, I so ran into the Nightmarish noise that seems to be common here. First I tryed to use the bluebox instead of my HU RCA's because I figured mybe it had something I needed but that didnt work. then I checked out this thread so I figured I would try the mod. I have no Idea what my output impeadance is but since I have 5 volt rca's I figured I would try 60 ohm. Radioshack failed me so I had to get some 68 ohm resisters but Im not sure if that makes a differance. I wired them in and found my noise to be gone but the volume was reduced by 60% or so. This I couldnt deal with, so knowing nothing about electronics I figured I could so the same thing with smaller resistors and I would be fine. I tryed some small 10 ohm resistors and had the same results as the 68 ohm resisters, no noise but low volume aswell. by this time somehow I managed to break the analog ground prong on the Scosche plug so I figured I would take the opurtunity to try something new. I bypassed the scosche plug for the analog ground by attaching my own 10 gauge ground wire to the RCA's, then I followed it down to the amp and connected the ground to the anolog ground wire right before the factory amp. My noise is now worse than ever, someone suggested that there is a ground loop, and if I cut a couple grounds and left only one I would be fine. I tryed unpluging the antenna and the analog ground but the noise just gets worse. someone else told me it could be AC coming through the circuit from the alternater and if I briged the positive and negitive lines from the alternator with a capacitor I could filter it. but I have no idea where in the circuit I would do this or what size capacitor I would need. any ideas?
Ive been without a HU for 2 weeks not trying to figure this out.

06-15-2006, 04:27 PM
You wanted to go the other way w/the resistors... Higher resistance value... rather than lower.

The recommended value from PacificBlue for 5V outs is 211 ohms = 500mv ... if you need more level... 475 ohms = 1volt

06-16-2006, 01:56 AM

Your Kenwood DPX-701 has three sets of HV PreAmp Outs at 5-volts: The two sets on the back are Front L&R and Rear L&R, the third set is a dual RCA cable marked Sub L&R.

Use 211 ohm resistors (270 ohms is stock off-the-shelf and will give slightly more punch). In your case I don't recommend using 475 ohm resistors as this will produce 1-volt out which may drive the StockAmp into distortion (it only needs 1/2-volt or 500mv and tests by board members show that 1-volt is way too much).

The Analog Ground (aka: Signal Ground) in the Scosche connector is essential. If it's broken, try to fix it or buy another Scosche TA-03 - it'll be well worth it. But you -must- keep the Digital Ground & Analog Grounds separate. Once you have the right resistors & grounds, noise will be history and you'll have plenty of sound.

Next, get yourself some subs.

Good Luck,

07-14-2006, 08:37 PM
vent had much luck with my mod, 2.2v preouts and I used 620 ohm (2% giveway) resistors, but I get weak sound, and nothing from the lows and little from the mids.... If I ground the resistor ends to the chassis instead, analog ground to the chassis I get all my sound back but with the typical deck/ecu/alternator noise...

I'm not sure where I've gone wrong, I've done the mod twice now, correctly. *bummed* I'm about ready to install a different amp altogether, but i really don't want to run new wiring :/

07-14-2006, 10:27 PM
ground loop isolators work well on getting rid of noise if you put them inline with the rca cables. i hate the blue-box thing that scosche sends. its such a pos.

07-15-2006, 02:57 AM

I see you've posted you have a Pioneer Pioneer DEH-7600MP deck with:

RCA Preouts 3 pair (Front, Rear, Sub or Non-Fading)
Preout Voltage & Impedance 2V, 100 Ohm

Hopefully you haven't tapped anything into the factory harness, like to connect an iPod or Carputer or something.

The resistor values you picked should work. Connecting the ends of the 4 resistors to Analog Ground (aka: Signal Ground) should work fine and sounds like they are, 'tho the sound is too low.

Make certain you are -not using the BlueBox- lot's of people miss this in the thread. The Bluebox has transformers in it which act like radio antennas to pickup alternator & ECU noise. Stick it under your back wheel and drive over it.

Connect the Scosche TA-03's RCA's directly to your HU's RCA's after mod.

Until we double-check your hookups, if you like... you can connect a 5th resistor in series with the ends of the other 4. In otherwords, instead of connecting the ends of the 4 resistors to Analog Ground, connect them to yet another resistor, say 110-270 ohms, then connect the loose end of that resistor to analog Ground. This should bring the level back up until we can figure out what's different about your setup.

But if you're going thru the Bluebox, you'll still pickup noise, it would also explain why your signal is so low.

07-15-2006, 10:50 AM
Thanks for the response Pacific, to clarify a few things:

I am NOT using the Bluebox
The TA-03 is hooked up directly to my HU RCAs
The factory harness has NOT been tapped into by any 3rd party device, or wire.

The best way I can describe my sound output, is like listening to an old AM radio - very flat, bland, with no life. Its as if, as I've mentioned, there's no bass and very little mid-level sounds being produced. If I tap the analog ground with a seperate chassis ground, I get all of my sound back, but with the nasty noise.

Like I said, I've done the mod twice over now, both with the same result. I've triple checked everything, twice over. Is it possible my Analog Ground wire is faulty, somewhere along the Toyota wiring behind the dash?

07-15-2006, 01:22 PM
"Is it possible my Analog Ground wire is faulty, somewhere along the Toyota wiring behind the dash?"

I don't think so because the level drops when you connect the resistors to it, which is what it's suppsoed to do (and you're probably finding out that you have to crank your HU's volume controls to near-max to get anything out of the speaker right?). And when it's not connected to Signal Ground your levels go up (probably even way too much and your volume controls are just barely off the lowest setting).

What you're describing sounds exactly like what happens when the termination resistors are too low in value. You might want check the color code on the resistors. With CarbonFIlm or MetalFilm Resistors sometimes it can be confusing cuz they can have up to 6 color stripes. If you used 620-ohm 2% tolerance resistors, the color stripes should look like this:

...6......2.......0.....xNone....2% + TempCoef (optional)

This based on this system:

A: first significant figure
B: second significant figure
C: third significant figure
D: how many zeros to add after (Black: None, Brown: 0, Red: 00, Org: 000)
E: tolerance in %
F: temperature coefficient in PPM

Here's a link to a webpage which explains how to read 'em and even has a visual calculator so you can see what it will physically look like:

07-15-2006, 01:38 PM
I purchased a pre-packaged set of 4.

NTE electronics 1/4w 620ohm, 2% tolerance, packet model# QW162 (link to PDF as reference

These resistors are
...6.....2........1.......2%.... (the Brown 1 means adding one 0 to the end, thus 62+0= 620)
According to the resistor references I've looked up, this is correct. Your BLACK where my BROWN is, is a 0 multiplyer, therefor there is no 0. So, your colour code of BLUE, RED, BLACK would yield a 62 ohm, not a 620 ohm. Correct me if I'm wrong.

So I truely believe I have the correct resistors... Perhaps your colour coding is correct, but you misinterpreted the brown/black at the end...maybe I should be using 62 ohm, and not 620 ohm?

07-15-2006, 03:12 PM
edit: sorry for the multiple edits if you read this early, my bad.

Your NTE QW162's are the right ones, 620 ohms.

I know, as I said it can get confusing... I should have mentioned the 3rd Significant Figure band is optional:

6 band color code:
...6......2.......0....(xNone)..2% + TempCoef (optional)

4 band color code:

Both color code systems = 620 ohms 2% tolerance but one band is dropped so the colors are shifted.

By the way, if the Multiplier Band is SILVER or GOLD, it shifts the decimal point to the left. For example:

4 band color code:
...6......2.....(x.1).....2% -> This is: 62 ohms x.1 = 6.2 ohms.

4 band color code:
...6......2....(x.01).....2% -> This is: 62 ohms x.01 = .62 ohms.

The tolerance (%) band is also usually a metallic color to distinguish it from the others and placed at the end of the band or 2nd from the end.

Anyway, your NTE QW162's are the right ones, so something else must be up. You might try adding the 5th resistor to see if it helps. I just don't have enough information to tell you exactly what value to use. If you've got an extra 620 handy, try temporarily hooking that up and see what happens. My guess is it will sound a lot louder and the noise will mostly be gone.

If you can post a pic of your TA-03 mod so we can see your connections, maybe we'll spot something.

07-15-2006, 05:39 PM
I put a 680 ohm in place after the 4 620's, same whine, ecu noise, etc.. but it is louder. I've been fiddling with other resistors too, can't seem to find something that works well.

07-15-2006, 11:54 PM
Just DL'd and read your DEH-P7600MP OP & INSTALL manuals. Your HU PreOuts are 2V 1000-ohm impedance not 100-ohm as spec'd on some websites. I see the Front L&R RCA jacks are in the back right next to an identical set of RCA's for SUB L&R Out (hopefully those didn't get swapped) and the Rear L&R are a pair of RCA cables hanging out the back.

I also see it has the ability to mute the system on command from a celfone, done by using the YEL/BLK wire - make sure this wire is capped, taped-off, not touching anything, and definitely not grounded. I see it's got AVL which you may wanna turn off during testing. It's got many EQ settings which if dialed-out might chicken-choke your sound. Other than that, it looks pretty normal.

(BTW, the 5th resistor should only be used for testing... you run the risk of "mixing" your 4-channels together back thru the 4-resistors & losing channel separation and stereo imaging if the ends of the 4 resistors don't get connected to Signal Ground. Also, don't connect the resistors to Chassis Ground, only Analog Ground).

07-16-2006, 06:38 AM
Yes, that all correct on my deck. I've always had the mute wire capped, and I've got the SW output capped as well so there's no confusion there. I could awlays have a faulty harness i suppose.

I hooked up an external PPI amp to the system and totally disconnected the stock amp... I get the same noice, which suggests there's a bad ground somewhere, and that is never fun to problem solve... I don't remember hearing noise when i first hooked up last week for testing...

07-16-2006, 08:28 AM
Alright, more testing *sigh*

So I pulled all the stuff from the stock amp, disconnected it all.

New PPI amp hooked up (very efficient, excellent little amp), bypassing the TA-03 RCAs completely, totally running speakers from the PPI amp, STILL getting the noise. So, this is not just a problem with the RCAs or resistors... there's a grounding issue somewhere, or there's some serious noise happening from a bad electornic device. I've checked my connections, it's good. Re wired the harness (it's starting to show, I might need to get another one, lol)

This happens with both stock and 3rd party amp:
Key at ACC: Clean, proper, no noise.
Key at ON: Noise, almost like a siren sound 'whee-whoo-whee-whoo)

This, therefore helps rule out the HU as the problem, since it would be noisy at the ACC position as well as ON. This also rules out the amps, for the same reason. There's a noise pick up with some other stock electrical device. I even upgraded my engine bay ground points with 4guage wires.

Interesting note: when key is at ON position, there's an electronic connector/sensor/whatever right underneath the intake manifold opening that's visibly heard. Not sure if this is normal or not, it could easily be since the 7th gen tends to be a noisy little car. Disconnecting this questionable device has NO impact however, the noise is still present.

I'd like to take it to a 'pro' bu tI'm not paying $80 / hr for some kid employees to trial-and-error all day.

07-16-2006, 11:08 AM
"I even upgraded my engine bay ground points with 4guage wires."

I'm curious about this. Depending on whether you "replaced" or "added" new ground wires & grounding points, make sure you don't have any loosely crimped wires at the connector terminals, or any loose screws bolting those terminals to the frame & engine. If you secured the terminals to any new grounding points on the engine or frame, the surfaces under the screws must be free of paint, rust, & dirt or they'll make poor grounds.

If the engine block's ground isn't electrically connected good enough to the frame's ground (& body), the noise from the engine ECU & alternator will come in over the 12-volt line from the alternator, thru the engine compartment, thru the fuse block, and into your HU & Stock (or other) PowerAmp like it normally does, but no longer have a decent ground in common to send the noise to.

I suppose you could try having someone poke a screwdriver between your battery's ground terminal and a bolt on the firewall while you listen inside to see if the noise level changes any. Also, corrosion between lead battery posts & terminals can cause noise in audio systems too. There are so many possibilities...

07-17-2006, 12:39 PM
You're right, there are too many possibilities ;) The 4guage wiring was crimped very well, and the ends were heat-shrink wrapped for stability. None of them are connected to the body's pain, instead they were designed to enhance/complement the existing thinner stock grounds.

I may not have time to fiddle with it further for a couple of weeks, I'm going on vacation... I'll just have to deal with the noise for a while! But if you have any more brainstorms let me know :)

08-04-2006, 04:12 PM
Have a Panasonic CQ-C7103U with ta03 hooked up...lots of whine when car is running none when car is off...

from the table i know i need 1/4 watt? 620 ohm resistors.

where do i get these?

08-04-2006, 04:22 PM
ignore that post i found it in the thread sorry

12-27-2006, 03:21 PM
Hi there PacificBlue,

I have a less simple HU I got and want to change out the GTS HU.

I got the Pioneer DEH2800MP model which only have one pair of preout RCA. and 50Watts X 4 speaker output.

I would like to keep the Factory AMP. How do I connect the TA-03 to the HU with only one pair of preout RAC ??

12-27-2006, 05:02 PM
You can do it a couple of different ways...

1) Easiest: Connect your HU L&R OUT's to RCA Y-Cables and connect the Y's to StockAmp Left F&R and Right F&R inputs (in the Scosche TA-03 harness). You'll have sound on all speakers, but won't have any Front/Rear fading.

2) Next Easiest: Connect your HU L&R OUT's to a 2-IN 4-OUT FRONT/REAR FADER CONTROL ( That's if you can find one. I found this one is in Australia.

According to the specs your DEH2800MP has 2.2volt PreampOuts, so you'd mod the TA-03 harness using resistors from the table for 2.2 volts.

12-27-2006, 11:47 PM
Hi, I hate to jump into the fray here, but I'm having a bit of an issue as well. I recently got a JVC KD-AR870 ( (woo USB!)

It has 5V@20kohm load (if I'm reading this right?) pre-outs. I get the alternator whine, a clicking when I have cruise on, etc... My problem is that I bought the HU from Crutchfield, which I have nothing but good things to say about, and they provided me with a wiring harness adapter (click) ( which doesn't quite seem to match the Scosche in some ways. I'm confused about how to go about modding this one. I'm actually considering grabbing another adaptor to muck around with so I don't end up killing this one.

In the chart, does the 5V row cover all 5V pre-outs, or does the impedance value matter?

Finally, I've blown the past two days mucking with this thing, and I'm kinda low on time starting tomorrow (year end rush... woo hoo.), would anyone be willing to mod up an adapter for me if I tossed in $10-15+parts for your time?

I guess I'm gonna have to put up with this until after new years either way, but thanks for reading and/or any help :D

12-28-2006, 09:23 AM
The harness Crutchfield gave you looks a lot like the Scosche TA-03 (except for the RCA colors) but I can only speak for the original TA-03 harness. (It should be noted the Scosche TA-03 has been replaced by the TA-03B and the price went up since I started this thread long ago {$33.95 as of 12/06}. Again, the Scosche includes the BlueBox LLC (Line Level Converter) which should -not- be used in this mod.)

One way to tell if the harness is the same is by using a DMM (Digital Multi-Meter) to measure the resistance in ohms between the Center Pin of any of the RCA's and one of the pins in the 20-pin connector. If it reads approx 1.9Kohms +/- 10% or so, then I'd say it's pretty much the same as the TA-03, and the Table of Termination Resistor Values for the mod should work just fine.

Click Here: For a table of Termination Resistor Values and Final Test Results (

In any case, most off-the-shelf wiring harnesses for the Celica will need to be modified. As a reminder, the whole purpose of this mod thread was to accomplish two things:

1) To drop your HU's high-voltage PreOut's down to approx 500mv (.5v) to drive the StockAmp to full output without distortion.
2) To drain the electrical noise picked up by the audio lines to ground before they reach the StockAmp.

"Among the potential sources of noise in the Celica are its multiple ECU's, cabin light dimmer, power windows, power sunroof, power doorlocks, front & rear windshield wipers, HID's, ignition system, alternator, and any aftermarket gear like neons, inverters, guages, etc."

It looks like the JVC KD-AR870 has 5-volt PreampOuts for Front & Rear, and 2-volt PreampOuts for Sub's. (and of course the wiring harness only applies to the StockAmp's Front & Rear inputs - your Sub Out's would go directly to an optional external subAmp and set of Sub's). You pick 5-volts from the chart and use the resistor which produces 500mv out.

Any volunteers in the Toronto area, or within mailing distance of Toronto who can do the mod for N-Bomb for some $pare bucks?

12-28-2006, 10:33 AM
Thanks for the help PB...

One more question, if I used the method 1) Y-cable, hows the sound quality on this setup?? I rarely change the fading F&R, but how will this change the High~Mid~Low characteristics ??

12-28-2006, 01:40 PM
Each HV LineOut of your HU is feeding 2v, 4v, 5v, 8v (etc, depending upon HU) at anywhere from 1k-50k impedance into two similarly high-impedance inputs (the modified Scosche TA-03 harness) before being terminated on the isolated-end of the mod's L-pad network.

Being a passive short harness, there's virtually no additional inductance or capacitance presented to your HU's signal as is passes thru the harness. In other words: the signal quality should be practically identical to the original.

Good Luck.

12-30-2006, 12:17 PM
I just got a Pioneer deh-p6800mp and installed it easily with the Crutchfield harness. I have the same interference noise and whine and it drives me nuts. The Crutchfield harness doesnt have the same grounds as the Scosche (analog, digital, chasis). The preouts from my head unit are 2.2v/1k ohms. So assuming the Crutchfiled and Scosche harnesses are the same I need around a 1/4 watt 633 ohm resistor?? What about the differences in the grouds? Should I just twist all 4 ends of the resistors and splice them into the ground on my Crutchfield harness?

Anyone completed this mod with the Crutchfield harness?? Any other ideas/suggestions??

I dont want to buy the Scosche one if I dont have to

Thanks in advance and happy new year!


12-30-2006, 01:43 PM
Good news - work finished early. Bad news - looks like my New Years plans have fallen through.

Well, it seems that the one Crutchfield provides is made by Metra (the name Metra is stamped on one side of the connector), and after dissassembly, looks like there are no resistors at all.

I bought a bunch of 200 ohm resistors, aiming at that 500mv sweet spot, so I hope the lack of existing resistors doesn't affect these calculations much! The wire lengths I'm working with here are kind of short, but so far no major problems.

Also I gotta say. PacificBlue, this thread's over 3 years old now, THAT is dedication, and we totally appreciate it.

(a few hours later)

Looks like a success! Well... it LOOKS like a sack of crap, but it... SOUNDS like a success! I had a hell of a time with this one - the wires aren't soldered to anything externally accessible like the Scosche, so I had to do some cutting and really iffy soldering. Also I couldn't get everything shrinkwrapped so I had to do some dodgy taping. My fingertips hurt.

The verdict: I need my audiophile friend to listen for a second opinion, but I don't think I can hear anymore alternator whine! Also, pre-mod the volume @ 3-4 would be about listening level, and anything louder than 6 or 7 would be too loud. At 1, you'd still have to talk over it if someone was in the car. Post-mod, 1 is actually QUIET, and good listening is around... 12-15? 20ish gets too loud. If this is all I've managed to do, I'd say I'm quite happy! Now I can finally get all the settings done and not worry about re-doing them, and re-setting the clock all the time.

Quick pics:

Resistors wired into pre-amp outputs (

The final product. Look at that lack of worksmanship :D (

@ thegregmizzou:
It's a real PITA to mod this one, my advice is don't strip off the heatshrink on the pre-out RCAs themselves because you won't be doing anything around them. You'll have to decide where to cut the pre-out +s, but about mid-way worked alright for me.

Finally, you'll only need the one analog ground to tie everything together, however, you'll need to add an extension bit to it, after unsoldering the the pre-out -s from it. I ended up leaving that bit bare, and re-attaching the pre-out -s to it, while using the other end of the extension to wire the resistors to (that's the bit of shrink sticking out perpendicularly from the rest there in the second pic).

Honestly, I think the Scosche would make doing this a ton easier, but it CAN be done on the Metra/Crutchfield, and I'm kinda glad now that I didn't spend the extra. I wonder if Crutchfield knows about this problem. Good luck!

12-30-2006, 01:58 PM
N-bomb/PB/everyone...thanks for the info. Havent tried it but will finally have a chance to after a vacation next week.

I called the Crutchfiled support line and told them what noise it was making and the dude on the other end said it was likely a problem with a ground. I ripped it all out, tried several different locations for grouding and was not able to fix it completely. This was a couple days ago and I havent called back to let them know or ask anymore ?s.

Ill be sure to be back on here and let you know how it turned out. For now I guess Ill just have to keep the volume loud enough to drown out the noise.

12-30-2006, 06:02 PM
It's DEFINATELY not a grounding problem. I was in denial about that before I wanted to try the mod and made a grounding strap out of some old heavy-guage speaker wire - didn't do a thing. The Problem only subsided after I did the mod.

12-31-2006, 02:44 AM
I'm glad you got the Crutchfield harness working, but disappointed to hear the 1.9k series resistor & some of the grounds are missing... Thank-you both for posting the new 411.

As many before have confirmed, the Scosche TA-03 Harness works great just by following the instructions at the top of this mod thread & very little else. Some have tried other brands of harnesses but with mixed results. If you don't like wasting time troubleshooting & wanna get this right the first time round, spend the extra bucks and get the Scosche TA-03 or BHA8113 harness. The manufacturers of Excedrin & Motrin will hate you for it, and your GF/BF, wife/husband will love you for it.

For the sake of clarification & to help everyone understand why "other" harnesses don't work, let me recap few things we discovered early-on about the significance of the different grounds Toyota used in the 20-pin R4 connector in Celica's equipped with the Premium Sound System (yes, there's MORE THAN ONE GROUND in the connector & harness) ... and then I'll talk a little about importance of the 1.9k series resistor in the TA-03 & BHA8113 harnesses:

"In the Toyota R4 connector (which the TA-03 plugs into) there are actually 3-different grounds:"

PIN-10 SGD3 (aka: DIGITAL GND, Radio-to-PowerAmp Wire Harness Shield, & is only connected to Radio side)
PIN-16 SGND (aka: ANALOG GND, RCA Signal Ground)
PIN-20 GND (aka: CHASSIS GND, goes to a real Ground Point)

PIN-10 & PIN-20 get tied together in the Scosche TA-03 harness because your HU only has one BLK GND wire.** The stock radio had separate grounds within the radio for CHASSIS GND vrs. WIRE HARNESS SHIELD GND.

**The Toyota WIRING HARNESS has a pair of ECU lines carrying Tx/Rx DATA to the StockRadio which is "NOISE" to the audio circuits, so Toyota/Fujitsu provided a separate SHIELD in the WIRING HARNESS and a pin to dump it to called "SGD3" aka: PIN-10 DATA GND. YOUR new HU doesn't have Tx/Rx DATA lines which connect to the Toyota Harness, so PIN-10 has nowhere to dump to - but because the WIRING HARNESS still carries Tx/Rx DATA from the ECU, it's important to get this SHIELD connected to ground and the best place to do this at the HU is by tying PIN-10 to PIN-20. And -because- it has some residual ECU noise in it, you -don't- want to connect this to PIN-16 RCA Signal Ground.

Click OrigPost: "couple more questions.... where does the digital ground go?" (
To give you a better idea, have a look in this pic.

Notice the three different grounds:
PIN-16 SGND (aka: ANALOG GND, or "Signal Ground" - this is ONLY for the shield's in the RCA's)
PIN-10 SGD3 (aka: DIGITAL GND, or "Wiring Harness Ground" - DATA GND)
PIN-20 GND (aka: CHASSIS GND, the "Real Ground" to Car Chassis for HU's Power BLK)

Also notice Scosche tied all the shields (copper color) from each RCA cable together and soldered them to PIN-16. They also soldered a short-length of BLK wire to PIN-16 (I called this the "U-Turn Wire" earlier in the mod instructions), which we use to tie all the ground-returns for the 4-termination resistors.

I believe the 1.9k (+/- 10%) Series Resistor in each of the 4 RCA lines in the Scosche TA-03 harness was put there originally to help isolate the HU output preamps from being damaged by any strange input loading caused by shorted cable or wiring error by an installer (worst that could happen is there would be no sound, but the HU would survive). We take advantage of it being there and add another resistor to form an L-Pad Voltage Divider to drop your HU's high-voltage PreampOut's down to 500mv (.5 volts). This is the level needed to drive the Toyota StockAmp to full-output without distortion.

To understand how both the 1.9k Series Resistor & _?_ohm Termination Resistor work together to accomplish this, have a look at the following webpage and enter the values below:

Click Here: Voltage Divider Calculator #2 (

Enter the following values into the calculator:

Vin = Your HU's PreampOut Voltage
R1 = 1900 ohm Series Resistor (already built into the Scosche harness)
Vout = .500 volts (what's needed for the StockAmp)
R2 = Is the value the calculator will give you for the Termination Resistors you need.

You can also find the value by using the table we made by clicking here:
TA-03 Mod Termination Resistor Values for HV HU's - Final Test Results (

As far as different makes of Wiring Harnesses go, we've seen 3-kinds:

1) Scosche: TA-03 / TA-03B Harness w/BlueBox LLC (approx $34)
2) BHA8113 Harness (approx $20)
3) Metra: 70-8113 Harness (approx $21)
Scosche: TA-03 / TA-03B Harness (approx $34)
(price also includes BlueBox LLC) BHA8113 Harness (approx $20)
Metra: 70-8113 Harness

We proven the Scosche works great time & time again, and seen good reports from those using the BestKits BHA8113, but we've mostly heard mixed results about using the Metra 71-8113 or "others" like it.

If you look back thru this thread you'll find a post by someone who bought the BestKits BHA8113 and verified finding series resistors inside just like the Scosche TA-03, while none were found in the Metra 71-8113 and "other" harnesses.

Missing series resistors, missing ground pins, and incorrectly wiring or combining grounds may result in doing little to get rid of your noise. I hope this clears-up any confusion as to why some harnesses don't clean-up the noise while the TA-03 does. To me, it's worth the $33 bucks for a harness we already know works for eveyone who's modd'ed it, and to know I'm not going to run into any surprises like missing series resistors, or solder-less pins using a substitute. I wouldn't want to have to spend hours troubleshooting because I used a harness different from the one in the original mod.

Besides, plenty of members have already done that for you, right?

Happy Mod's & Happy New Year!

R K e 1 C A
01-04-2007, 06:38 PM
PacificBlue could you assist w/a Clarion ADX 5655z

<---- audio :newbie:

01-04-2007, 10:55 PM
Reply to your PM sent.

01-15-2007, 05:55 PM
I'll try to keep this short...
I was anxious to mod my Crutchfield/Metra harness and didnt take the time to do the complete/proper math on the resistors needed. I used the chart posted earlier in this thread and went with 470 ohm 1/4 watt resistors because thats what I could get from rip shack and was the closest to what I would need for 2 volt pre-outs. Put the resistors in with the rca cables and into the ground similar to what n-bomb had done (no pics of mine though). It looks like a mess of butt connectors, solder, heat shrink and tape but did the trick. Mostly.
When I was putting the head unit back in after the mod I noticed I could still create the theremin effect. Not as easily as before the mod, but when the engine was running and picking up the noise it seemed worse. I put it all back in there and it was fine. No interference and the whine was 99.6 % gone. Only time I could really hear any noise was when I was switching sources or the volume was at 0, and there was no signal going into the amp.
Now a week later, when everything is good, its great, but Ive noticed that bumps or crossing railroad tracks can jar my mess of wires and bring back the interference worse than ever. I havent taken the time to pull it all out again and check the connections and secure everything, thats my next step after this nasty weather clears out.
Thanks again to everyone for their help!!

01-24-2007, 12:22 AM
I just bought the TA-03B the new version and came into some problems.

The harness is redesigned with a longer harness piece(the white box that connects). The wire seems to be clamed down to the pins instead soldering to the pins. There are extra wires that comes with it....


PB, can you tell me what those extra wires are for ???

I assume Blue/white goes with blue/white, Red with Red, and Yellow with yellow......

Thanks for the help...


I know the black/white and black goes to the harness ground.

01-27-2007, 02:45 PM
I've hit another roadblock.

I have a 03 GTS with the power antena. After I pluged everything in my power aneta stop working. I connected the blue/white cable with the radio harness blue/white cable and the power antena doesnt come out when the radio is on.

However if I disconnect the blue/white cable, I get no sound.

So on the TA-03B harness. I got 2 extra wires.


Does anyone know how do I get the power antena working ??

The HU harness only comes with.

Yellow: POWER
Blue/white: Remote System or Antena Relay
the rest are speaker wires.

Can someone help ?????

01-28-2007, 03:42 AM
your remote/antenna relay is your power antenna source(blue w/ white stripe), and the orange is standard color for dimming wire. Does your head unit have a dimming feature?

01-28-2007, 01:39 PM
your remote/antenna relay is your power antenna source(blue w/ white stripe), and the orange is standard color for dimming wire. Does your head unit have a dimming feature?

Hey Vegeta,

Thanks for the help. My HU donesnt have that dimming feature.

I did connect the blue/white with blue/white and my antena doesnt pop up when the radio is on.

and I tried to unplug the blue/white cable and I get no sound at all.

and another thing the new design of the TA-03B is F'ed up. They used the those reistors as the start of connection. Not the adding more reisitor is nearly impossible.

I took out the old resistors but with a 2.2v pre-output HU, how much resistor ohm do I need all together since I've removed the one that came with the Harness.

Anyone can help ??

01-29-2007, 12:34 AM
I wish i knew more about the resistor mods to the harness. I didn't want to hassle with finding the right harness on my gt-s so I just opted to put components in the door and run new wire up to the dash for the speakers. Then I just tapped into the stock harness without cutting it and found a 12V+, switched 12V+, and ground. Hooked up my rca's, ran the remote wire to my amp, and called it a day.

Crystal clear from day 1 through today (3+ years later), to me this was much easier(and better sound quality) than going with the harness.

sorry i can't help you more...maybe pacific will show back up and answer your ?'s

02-01-2007, 10:37 PM
man, I am getting A LOT of ECU noise just like Syns...

no matter how much resistor I put I can hear the ECU noise.....

if I pull out the ground wire, the ECU noise X10....

Does anyone else having this problem ?????????

02-08-2007, 02:24 AM
Pinchy, sorry I missed your PM... Thanks for the pic of the TA-03B, and yes I see they connected the series resistors directly to the 20-pin connector and added some new wires.

Have a look at this post I put up back in August '02, It lists the pinouts and functions of every wire in the Toyota R4 20-pin Connector that the Scosche plugs into:

To make this work, you might first try exposing the series resistors by slitting the black heatshrink around them. If possible, solder one end of each mod resistor onto each pin, or over the end of the series resistor where it's crimped to the connector pin.

Next, twist the other end of all four mod resistors together and solder them to a short piece of wire. Solder the other end of the wire to Pin-16 {formerly known as the Black "U-turn" wire}.

Now test the harness. If all goes well, go ahead and seal the harness with RTV silicone sealer or similar. Cut-up some leftover stiff plastic from some product packaging into a 3" wide strip that's long enough to wrap around the connector. Mark & cease the folds, wrap it around the connector, and tape it off. Inject RTV around the exposed resistors and fill the mold, After it sets you should be able to peel the plastic away,

Use the Pinout diagram above to figure out what each new wire connects to. Post your results & progress here or you can PM me.

02-09-2007, 10:25 PM
Can you tell me what kind of resistors I'm going to need for the Alpine CDA-9853.
Car is Celica 2003 GT-S.
And what mean every color of this:

05-14-2007, 09:20 PM
well i skipped the whole ta03 harness and went strait wire to wire install... had the buzzzzzzzz... so i read my stereo manual.. 5V 100ohm preamp.... so i went to the shack and got 100ohm resistors... put em in and almost completely eliminated the whinessssss... so im gonna step up to 270ohms and see what happens.. to try to eliminate the buzzzzzzzzzz completely.... but i also noticed the HIGHS get chopped in my pezo tweeters.. and there is not nearly enough bass with the 100 ohms.. so ill report back with the 270 results... :monkey:

05-14-2007, 09:32 PM
here you go as per pacific above....

Wiring Harness Color Codes & Pinout for Toyota HU 20-pin R4 Connector:

1 BATT = BLU w/Yel Stripe*
7 Mute = Brown
8 FrtR = Red
9 FrtL = White
10 Shield (drain wire)
11 ACC = Gray*
12 FACTORY RADIO ONLY = WHT w/Grn Stripe* (Don't use! Cover w/tape!)
17 Beep = Green
18 RrR = Blue
19 RrL = Yel
20 GND (car chassis) = BROWN*

*1, 2, 3, 11, 12, & 20 (in caps) are individual wires, the rest are shielded together (pin 10)

05-15-2007, 12:09 AM
Oh men!!! Why did I not search here first!!! I just got a new amp because of that noise crap!!!

07-18-2007, 06:04 PM the new version of the TA-03 uses 2.2K ohm resistors instead of the original 1.9K ohm and will slightly change the resistor value for the mod.

Use the link posted by PacificBlue:

For the newer version, enter the V out of your HU in Input Voltage, 2200 for R1, and 0.5V for output voltage to get the correct value for the mod.

07-19-2007, 07:55 AM
So has any one had any luck doing the mod on the new design of the TA-03. I want to buy one but don't want to waste my money if you can only do the mod on the old design.

07-19-2007, 09:28 AM
Has anyone had any luck doing this mod while still USING the blue box? I have an older head unit with only one set of 2V outputs (which are used for my subs). Would I still perform the same resistor mods to the harness? Or, would this be useless because no matter what I do to the harness, the blue box would still pick up noise?

07-19-2007, 12:07 PM
Thanks to whoever PM'd me, looks like I missed a couple of forum alerts notifying me of new posts here.

It's not that the new style Scosche TA-03B can't be modded, it's just that the older TA-03 was much easier to work with because it had exposed pins. It's probably safe to say the new TA-03B was designed as an improvement to the product by making a shroud for the exposed pins which helps protect them from getting snagged, ripped off, or shorted-out on any sharp objects behind the dash. Unfortunately for us, this makes getting to the pins a little harder.

"The eXacto knife is your friend" when working with the new connector. Basically you only have to slit the black heat shrink covering the hidden 2.2K resistors (TA-03B) to expose the side of each resistor connected to the connector's pin. Here you'll connect one side of one termination resistor per channel, then tie all four "free" legs of the termination resistors together and connect them to the black SignalGround wire as described above.

As far as values for the termination resistors pick the value from the Table earlier in this thread. If using the TA-03B (not TA-03 orig) you should use the calculator I posted, or you can add +16% to the value from the table. For example if the table tells you you need a 211 ohm resistors for a TA-03 orig, add +16% when using the newer TA-03B or 244 ohm resistors.

As one of you complete a successful mod of the TA-03B, you should post a pic or two here so others can see your technique before sealing it up.

And btw most of you have been great but a few of you might want to utilize the forum's Search Engine a little more. I know this thread has gotten fairly long over the years since I first started it, but just about everything you need to know has already been covered in it by many of our generous members who contributed. And only because it's important I'll post it again:


If you want an explanation, search for "Bluebox".

Goor Luck.

07-25-2007, 06:26 AM
I am getting my harness and can post some pictures on doing the noise mod on the new design. But anyone have any suggestions on where to buy resistors? I tried radio shack but they didn't have any values between 620 and 1000. I need somewhere around 720. Thanks.

07-25-2007, 09:22 AM
Check your local Yellow Pages for "Electronics Distributors" or "Electronics Parts". Crutchfield is HQ'd in your hometown and has a Retail Store that might have em or know where to get them. Click the following link to scan your city for a bunch of possible places, scroll half-way down to "Local listings:" (in black ink):

Charlottsville, Va - Electronics (

07-26-2007, 05:57 PM
Which Harness is this? Metra TYTO01... I have a 2000 GTS and want to hook up a carputer with 4 channel audio out to factory amp WITHOUT a HU at all.. putting a 7" touch screen in it's place. Any recommendations?
Is the TA-03B what I need?

07-26-2007, 06:17 PM
Pacific Blue
I ended up just buying 680 ohm resistors. My head unit has 2.2v output and according to the chart +16% because I am using the new TA03 harness I need ~720 ohm resistor. I couldn't find 720 at radioshack or anywhere else and don't feel like ordering online. Do you think I will be able to get buy with a 680 ohm? Or do you have any other idea. Thanks for your knowledge.

07-26-2007, 11:45 PM
ber2z: The 680-ohm resistors should be just fine.

doyetgenev: It looks interesting, but according to Metra's site the TYTO01 was designed for later generation Toyota's. So far I haven't been able to find any decent product specifications which might tell us more. If you scroll-up, you'll find pics of the various harnesses including their PN's, descriptions, and warning about the Metra not having any resistors.

07-28-2007, 08:18 PM
*Repost (need feedback)*

I just recently bought an after market HU, a Pioneer DEH-1900MP, to be exact. I bought the install kit, the ISO/DIN mounts. And was sold a Toyota/Scion 1987-up turbo-wire harness, only to realize that it did not fit the stock radio wire harness. Only to then later realize that, that is because I have the premium sound system, with the stock amp. So I ended up returning the wiring harness, but now i don't exactly know how to bypass the amp myself. I was just wondering If I wanted to bypass the stock amp entirely, would the Scosche TA-03 do the job? Or am i better off doing this mod to use the stock amp with the after market HU? any feedback is welcomed, thank you.

If someone/anyone could PM me or email me with what I should do next. I have the HU on hand and ready to go, I can't wait to get it in, But I don't know what my next move should be. Once again, some help would be greatly appreciated.

07-29-2007, 10:05 AM
IMO, since you have the stock amp I would just get the TA-03 and perform the mod. That is what I am doing once the damn thing arrives in the mail.

07-29-2007, 11:24 AM
OK, Well I ordered the new TA-03b, with the 2.2k ohm resistors, so by using the calculator provided, i figured i need 647.06 ohm resistors, right? well anyway I'm not too experienced with electronics (resistors, and soldering etc.) But I know someone that could help so I'm expecting this mod to go smoothly. Will post with results.

07-29-2007, 03:46 PM
To help new visitors to the TA-03 Noise Mod Thread find the latest information more quickly, I've updated both the original mod post and the Table of Termination Resistors post with the latest 411.

The updates note changes in the termination resistor values for the newer TA-03B harness, the compatibility of BHA8113 harness, and the brand-new Metra TYTO01 harness.

Incidentally, as mentioned in the updates the BHA8113 may still be using the older-style TA-03(A) connector shell which is much easier to mod than the newer TA-03B. There's one Seller on eBay who seems to stock a bunch of these at a great price. If you want to check him out here's a link to search his store: Search Store for BHA8113 Harness ( 0ConnectionQ20CarQ20AudioQQfsooZ1QQfsopZ1QQftsZ2QQ saselZ27162071QQsofpZ0)

07-29-2007, 08:43 PM
Hey, thanks Pacific Blue for being so compliant and helpful. I'm definitely glad I came across this site, i don't know what i would have done, thanks for everything! And I'll be sure to frequent this site. :D

07-30-2007, 08:19 PM
Well got my TA-03B and even though I was really careful ended up cuting 3 of the 4 wires that connect the resistors when I was cutting the heat shielding. The TA-03B sucks big time and now I have to spend another 30 bucks because the harness is ruined. Be really careful when cutting the shielding back to expose the resistors.

07-30-2007, 10:32 PM
Hmm, well thanks for the insight. I should be getting mine this Friday, so i hope not to have any difficulties.

07-31-2007, 04:48 AM
I decided to buy the harness since it was only 15 bucks on the link that pacific posted. There have been good reports with this harness and it has the design of the ta-03a which is much easier to mod. I haven't really heard any good reports with the ta-03b. (good luck spartan I hope it works) I could have done it alot easier if my dumb self didn't accidentally cut a wire but unless you have elf hands I would suggest the bestkits over the ta-03b.

07-31-2007, 07:52 AM
I just got done reading all three pages to try to educate myself to the fullest extent. I have the pioneer deh-p6800mp (,,2076_4039_291078777,00.html) and the CD-IB100II (,,2076_310069910_307492523,00.html) which allows you to control the I-pod from the head unit. It also charges the ipod. There is an IP-BUS cable that plugs directly into the back of the HU. There are two other wires. One connects to "the terminal always supplied with power regardless of key position." This wire has a fuse in the middle of it with (2A) in parenthesis. The second wire just connects to metal ground on vehicle. Hope that makes sense. I am planning on buying the harness and doing the mod with 620 ohm resistors since the output is 2.2v on my HU. Is having the CD-IB100II going to screw anything up or should the mod work fine. Anyone have a similar setup or and experience or input is welcome.

07-31-2007, 11:25 AM
Hmmm well good luck man, I hope I don't have to order another one :\ I just want this done with. And no I don't have Elf hands, I have Spartan Hands!!! ahahahah so maybe ill beat the harness into submission? :P well Idk I have a friend and his dad builds circuit boards for repeater radios, so he's pretty experienced with this stuff, and he should be able to do it. And if he breaks it I'll see if he'll buy another one, ahahahaha well anyway Lemme know how the other harness works out, ber2z.

07-31-2007, 11:32 AM
With so many reports about modifying the newer TA-03B being difficult and the price increase from $25 to $35 I decided to see if there's a better solution. When posting the eBay link for the BestKits BHA8113 harness, I also ordered one to test. So I'll post my evaluation here as soon as it arrives and I've finished testing.

07-31-2007, 12:13 PM
I hope I can get it done, with out ordering another harness. I will try to document the modding, if successful, and will post some pics. But I'm eager to see what you can do Pacific, keep up the good work!

07-31-2007, 02:29 PM
Any body know if connecting the Ipod adapter in my above post ^ is going to screw things up?

07-31-2007, 09:46 PM
Pioneer has always made some nice accessories, and the CD-IB100II iPod interface is no exception. It comes with a standard iPod Cable which you can plug directly into your iPod or if you've got an extra dock handy, plugs directly into the back of the dock instead of your USB cable.

Everything is pulled thru the docking cable so you won't have to run a separate cable to the headphone jack on the iPod. Once your Scosche/BestKits harness is installed, whatever audio source you select on your Pioneer DEH-P6800MP HU will be output thru the harness to the StockAmp.

Nice system, I love how it interfaces & displays the iPod menus on the HU's display. Very cool.

08-03-2007, 04:31 PM
Good news Boys & Girls... $16 and a fast shipper later I've got the BestKits BHA8113 harness in my hands, and looks identical to the Original Scosche TA-03 connector & harness. My DMM here at work says the internal series resistors measure 1990 ohms (within +/- 10% tolerance for 2K ohms) and I can confirm the pins are nice & long with heatshrink on them, exactly like my original photos at the beginning of this thread. Also, at $16 delivered there's no BlueBox to drive the price up higher.

Conclusion: In lieu of the Scosche TA-03 (original) which has been replaced by the not-so-easy to work with TA-03B, please use the BestKits BHA8113 harness instead.

Happy Mod'ing Everyone!


08-03-2007, 07:05 PM
Alright, just a little update:
First off I got my TA-03B in today, and insisted on getting my radio in. So I went to a friend's house, his dad makes circuit boards for repeaters, so he was much more experienced than I was, and thus made it a lot easier. So if you haven't done this kind of thing yourself before, I highly suggest making a friend whose father is an electrical engineer :D It can be done, from what I saw, him actually doing the work it wasn't that hard, you just have to follow the original plan, and be very careful. So i got it mod-ed, with a 130 and 470 ohm resistor combination, to make it 600 ohms, close enough to what I needed to make it exactly 500 mV (647.3 ohms) so the mod-ing went smooth. I have some pics if anyone is interested, I forgot my actual camera so there $hitty quality phone pics, but better than nothing :\
Installation was another story, my HU only had two RCA out-puts for the rear speakers, so I was forced to use the blue box. At first I wired the speaker outs into it incorrectly, but then just swapped em, and that was fixed. I still haven't mounted the blue box securely, still possibly tuning it. But with the mod-ed harness and Blue Box, I didn't hear any buzzing, humming, or any noise at all, but maybe I wasn't listening well enough... Anyway the only difficulty I have with the blue box is that if I flip the switch to "Factory Amp" or "Common Ground" there's no sound, so I left it on "Line out" and it's fine.
Other problem, the rear speakers seem more timid than the front speakers, having to turn them up a lot more than the front speakers, to equal the volume. Not sure if the resistors are causing that, and if so, why hasn't it affected the front speakers? So If someone could offer some advice or insight on that problem, that would be greatly appreciated.
Another final problem is a "pop off" idk if I'll just have to get the SPSOFF to solve that or maybe some re-wiring can help. Once again, thank you all for your help and feedback.

08-04-2007, 01:26 AM
First, congratulations on getting your TA-03 modded. Second, I'm not sure I understand when you say "my HU only had two RCA out-puts for the rear speakers". Full use of the TA-03 harness & Toyota 20-pin connector involves connecting 4-RCA's for FrtL + FrtR plus RearL + RearR.

If your HU only has 2-RCA's (LEFT + RIGHT), you could try using an RCA Y-Cable plugged into each channel and connect one leg to the front, one to the rear, and repeat using another Y-Cable for the other side, but the level may be too low since you'd be terminating each channel thru the harness twice, aka: "double-termination". If you have to crank the HU to max to get decent level, you'd basically have to double the value of the terminaton resistors used. For example: instead of 600-ohms use roughly 1000-1200 ohms to conteract the double-termination. (I'm too tired to do the math, but technically the 1.9k series resistor helps prevent this from having the same effect as a true double-termination, so doubling the termination resistor value should easily compensate for the loss.)

And guys, I can't overemphasize the importance of throwing the BlueBox out the window if you want to connect an aftermarket HU to the Toyota StockAmp. I never went into all the reasons why it's a headache, but yes as you're experiencing, distortion of the frequency response curve through cheap passive capacitance/inductance/transformer-staged coupling is one of the side-effects when compared with using direct-coupling which is what the harness uses. It is -not needed- for connecting a 2/4-channel LineOut HU to the 4-Channel StockAmp, and in fact will only add noise and alter the frequency response of your HU's clean signal.

09-10-2007, 11:09 AM
Hey guys, I really don't know much about electricals. But since I'm going to put a new kenwood HU in, I'm trying to figure out what I need in order to get it to work on my 02 gts.

So from the HU manual, I got these specs...
Preout Level (V) : 2V/10k ohm
Preout Impedance : 600 ohm
Speaker Impedance: 4-8 ohm

So I'm looking at this thread. Since I have a 2V preout, it seems like I'll need 633 ohms resistors (+16% for ta-03b). But my question is, what does the all the extra ohm values mean on my specs? So say Preout Impedance, since it's at 600ohm, do I take that into the equation meaning I only need to add 33ohms resistors to get the 633ohm recommended in this mod?

And also, what does the 10k ohms from the "2v/10k ohms" spec mean? Any help would be greatly appreciated.

Thanks in advance guys!

09-12-2007, 10:29 PM
Just lookup your HU's HV Output Voltage in the table and use the resistor value listed in BOLD.

The "active impedance" of a signal source is measured in ohms but doesn't necessarily match that value when measured with an ohmeter. For example your HU has 600-ohm PreOuts, however won't necessarily measure 600-ohms across the PreOut's when measured with an ohmeter.

This is because "impedance" is a complex quantity which represents a circuit's opposition to an AC (alternating current) signal and its phase. It's calculated mathematically.

The receiving-side of the system (StockAmp) also has an impedance (approx. 1M aka: 1 million ohms) which is a total mis-match of impedances. Therfore we couple the source & desitnation thru an L-pad antennuator network formed by the 1.9K series resistor and a mathematically chosen terminating resistor whose combined value is equivalent to the output impedance of your HU, placed as close to the input of the StockAmp as possible (in this case inside the TA-03 or BestKits harness).

09-13-2007, 08:45 AM
Wow, that's as comprehensive as any answer can possibly get! Thank you for taking the time to explain that to me! I guess I have one final question for you. Say I cannot find one 600ohm resistor, can two 300ohm resistors soldered together in parallel on the harness achieve the same result as one single resistor of equvialent impedence?

10-17-2007, 12:30 AM
:wiggle: Okay I just built my carputer and slapped that joker in my GTS. I measured the output voltage of my soundcard and got 2.2V. So I needed to drop it to 500milivolts... easy enough. I first purchased the Scosche TA-03B harness and modded it accordingly. Yes, using the new resistor values- but had whine. Boooo! I believe it may be because of the structural compromise of the connector which is necessary to mod that one. I cut away the bare minimum to access the pins for soldering with a fine tip iron, used flux etc. But the connection didn't seem secure. I then bought the BHA BestKits harness and modded with 560 ohm resistors and BOOYA no whine and perfect audio. PS... an 8 inch touchscreen really fits perfectly in the dash. Thanks for all the help in ere folks!

10-17-2007, 12:38 AM
Wow, that's as comprehensive as any answer can possibly get! Thank you for taking the time to explain that to me! I guess I have one final question for you. Say I cannot find one 600ohm resistor, can two 300ohm resistors soldered together in parallel on the harness achieve the same result as one single resistor of equvialent impedence?

You should put the resistors in series. Heat shrink over both for support.

12-27-2007, 01:25 PM
Ok I'm confused.

2000gts getting alternator whine.

Line out level/impedance
2.5V/20k ohm

I have the metra harness from Crutchfield (Never had to deal with these new systems with my old cars 'sigh' )

How can I do the calculation if the I don't have any resistors in the harness? If I put in 0 I get 0.

02-09-2008, 08:03 PM
Scroll up a few posts and order the BestKits BHA8113 harness from the eBay search link I posted prevously. He still sells them, but now they're only $9.95 As mentioned before, the Metra has no series resistors so it's useless unless you want to take the time & trouble to add them yourself.

The BestKits BHA8113 Harness is identical to the now-discontinued Scosche TA-03A originally used in this mod and is the only harness I can recommend to take its place. Good Luck.

05-12-2008, 05:26 PM
In the BHA 8113 I purchased from the ebay seller that you linked it has the resistors right in the front as opposed to hidden mid wire. Where then do i unsolder from the pin? Thanks for your help.

05-26-2008, 12:46 AM
I just bought my pioneer headunit and am getting the whine like everybody else. Instead of using the BHA8113 with RCA's why don't people just use the BHO8113

It just doesn't have the RCA's. instead of taking the extra time to find the resister values and what not, why don't they just use this wiring harness and connect the wires togeather instead of just plugging RCA cables in.

Im not sure about anybody elses HU, but mine has RCA out's but also regular + - line outs for the speakers aswell. For others like this would the BH08113 be an alternative choice or will it not work for any reason I am overlooking?

05-26-2008, 04:54 AM
What you're missing is that the BHO8113 is a reverse plug to use when you are installing an OEM radio INTO something else. Not for putting an aftermarket into a Celica.

05-26-2008, 07:44 AM
duh ha

Thanks :)

05-26-2008, 01:51 PM
Np ;)

06-03-2008, 01:42 PM
I did this mod with the BHA8113, and like theeocho said the resistors are soldered directly to the pin itself, I tried to solder my 330ohm resister to the resister/wire connection but now I get this loud eeee/oooo eeee/oooo when the car is in Acc as before the mod was done I didnt hear anything unless the car was turned on. Also note that I havn't really heard a difference other than the whining that is now coming through when the car is in Accessory mode. I'll have to play around with it some more, anybody have suggestions? Is this because I have taken off the plastic shielding over the wires and have not put any back yet? so there is some sort of interference? instead of headshrink tubing I just used electrical tape is the shrink tubing a must?

06-21-2008, 01:46 PM
I purchased a VR500CS-BT for my 2001 GTS celica. REmoving the old one was a "snap" but know I"m stuck.

I have this harness: BHA8113

On the back of the VR500 there are 2 rca jacks called line out. Do I just connect the rca plugs from the harness to them to connect the speakers? If not how do I connect the speakers?

Also, I don't need to mod it, right? (If I do I am willing to pay for someone to mod mine.)

Thanks for all your help.

06-22-2008, 11:31 AM
You need to mod the harness for the correct input level to the amp. If you only have 2 Line Outs (L & R), you'll also need to join the harness' front & rear inputs to connect to the HU's Line Out. You will lose front-rear balance this way. Another option is to use the speaker outs and much different resistor values for the mod.

p.s. you need to add your location info to your profile.

06-22-2008, 03:20 PM
That's ok if I lose the front and rear balance.

Dude, I can't mod anything outside of adding decals to my car!

Is there any way I can do it without a mod?

Also, there are speaker wires coming out from the radio, could I cut the harnesses rca cables and connect them manual?

PS: I added my location! Anyone in the area who could help?

06-22-2008, 03:48 PM
Dude, I can't mod anything outside of adding decals to my car!lolIs there any way I can do it without a mod?Niot really w/an '01.... you either mod to use the amp, bypass the amp & mod the front speakers, or replace the speakers..there are speaker wires coming out from the radio, could I cut the harnesses rca cables and connect them manual?Another option is to use the speaker outs and much different resistor values for the mod.^Yes.

06-22-2008, 05:10 PM
Thanks for all your help is much appreciated. 3 more quick ?'s if you don't mind.

1.So what if I just took it to a place that installs car stereos, they could do it for me right?

2. If I mail you the harness can you mod it for me for some $$.

3. When you say mod the front speakers, (remember I'm mechanically inclined :'), do you mean or can I just run speaker wire from the HU to them? (or better yet disconnect the from the stock amp and run them right to the wires on the hu?)

4. will this harness work without needing mod? Metra 70-8112


06-23-2008, 05:17 AM
1.) You would probably have to take it to a shop w/Mobile Electronics Certified Professionals (MECP)... not the neighborhood BB... and provide them with the info in this thread.

2.) Not something I normally do. There might be someone else on the board willing to help you out with that.

3.) Bypassing the amp, speaker outs from the new HU to the old outputs from the amp (disconnected from the amp), and rewiring the woofer in place of the mid-range in '00-'02's.

06-23-2008, 01:31 PM
Thanks again...
I think I"m going to go with option #3, bypass the factory amp.
I"m not sure what you mean about re-wiring the "woofer in place of the mids" I have a 2001.

so long as I just hook the hu speaker wires to the actually speakers and bypass the amp I should be good to go! I think :monkey:

06-23-2008, 02:36 PM
You'll lose low end if you don't re-wire the woofer in place of the mid range.

06-26-2008, 02:41 PM
Just finished install. Used the y adapter and harness. I did not modify the harness. I get that feedback sound as everyone described. Also the sound destorts "slightly" every minute or two for only a fraction of a second.

I have to say I love the bluetooth phone feature.

I'm going to see if it bothers me or not...and if it does then I will have to re-route around the amp!

I wasn't sure where to hookup the amp turn on, so I just connected it to a speaker wire. Is that what I was supposed to do?

Also I forgot to hookup the amp ground. Is that OK?



06-26-2008, 03:38 PM
Also I forgot to hookup the amp ground. Is that OK?

No it isn

06-26-2008, 08:26 PM
Well I thought I had it down pat and the noise gone, it seemed to go away after I grounded the amp, but as I began driving the whine gets louder as the rmps of the vehincle increases.

Any idea what is causing only happens when the vehicle is running and get progressively worse as rpm's increase.

06-27-2008, 07:11 AM
Can anyone help me with running directly around the stock amp? Again, I'm freakin clueless. I guess I don't need the rca cables then? Can I just use the wires?

Does anyone know what the wires are coming from the speakers to the stock amp?

06-27-2008, 11:56 AM
Metra sells a harness for the amp to bypass it (Amplifier Bypass 70-8118). You can try that. Like I said, you'll lose the front subs and will probably want to rewire them in place of the mids. We can cross that bridge later, though.
but as I began driving the whine gets louder as the rmps of the vehincle increases. Due to not doing the resistor mod.the sound destorts "slightly" every minute or two for only a fraction of a second. Ditto

Idiot Stick
06-27-2008, 12:32 PM
So looking at the guide, I should be using 271ohm resistors...Does that mean a total of 271 ohms or get 4 of them at 271ohm's? So I'd probably be shooting for 300Ohm resitors, since my deck is a 4v Pre-out voltage.

So yeah, does that mean I gotta get 4 to add up to 300 Ohms resistance, or get 4 of them at 300ohms?

Sorry for the very dumb question :)

06-27-2008, 03:19 PM
(4) 270 ohm 2%, 5%, or 10% tolerance resistors. (1) for each of the four amp inputs: FL, FR, RL, RR, as shown in PacBlue's 1st post in this thread.

Idiot Stick
06-27-2008, 03:24 PM
Awesome. Thanks 2way.

07-03-2008, 11:41 AM
I was just finishing up my install when I accidently grounded a wire that I wasn't supposed to. A little bit of smoke came fron the wires and I heard a pop.

I went to the fuse box and found one fuse was bad. I replaced it but the radio does not work nor does the original stock one. Please Help!!!!

07-03-2008, 02:04 PM
got it fixed...I didn't know there was another fuse in the engine compartment. To make a long story short, I was able to reduce the noise to an "acceptable" level. Until I can get someone who will modify the harness for me.

Thanks for all your help especially 2way!

07-04-2008, 05:51 PM
Just me again....
Just wanted to verify:
Black to Black (ground)
I have two black wires with white stripes:
I grounded one to the chasis. (Once I did this noise feedback was reduced)
What is the other? What should I do with it?

Idiot Stick
07-07-2008, 11:37 AM
I just picked up a BHA8113 from Futureshops Audio Install garage, and it looks like they have resistors shoved into the lines already? Is this supposed to look like that? Im gonna try the install without the mod to see anyway, but it looks nuts. Maybe Bestkits updated the harness?

07-07-2008, 12:02 PM
^ You need to re-read this thread........ more closely.

Idiot Stick
07-07-2008, 02:23 PM
^ You need to re-read this thread........ more closely.
I can't beleive I missed that part. Wow.

Doin the mod tomorrow - the store is closed now. Psht.

07-07-2008, 06:00 PM
Idiot stick, can you mod one for me if I ship it to you? (after you test yours of course)!

Idiot Stick
07-08-2008, 03:47 PM
Idiot stick, can you mod one for me if I ship it to you? (after you test yours of course)!

Lmfao. I just tried mine and ****ed it up somewhere. The Bestkit ones are horribly different in the sense you cant pull the pins out to get rid of the original resistors. Plus im terribly impatient. So somewhere in the mix, my problem was no solved by any means, and the front left speaker wasnt working.

...putting my OEM deck back in till I can get some professional to do it.


07-08-2008, 06:15 PM
Umm, you don't get rid of the original resistors. Better read better;)

07-08-2008, 06:25 PM
How/Where in the world do I find a Mobile Electronics Professional?

I will probably have a better chance of stumbling across a four leaf clover, or even a leperchaun with a pot of gold :)

Idiot Stick
07-09-2008, 03:19 AM
Umm, you don't get rid of the original resistors. Better read better;)

I couldnt get far enough in there to remove the originals. I might get bored again today and giver another shot though. The harness cant get anyworse, lmao.

The four speaker wires are all interconnected by what seems to be the Analog Ground, and where I couldnt physically move the pins back it made it that much tougher. The original resistors are right after the pin, so getting to that alone would be a gong show of its own.

Looking at the first page, it looks like you should have our resistor mods before (Closest to the plug) the original resistors, or strait out remove them from the equasion.

07-11-2008, 12:02 PM
After reading multiple posts very closely, if I'm correct one is digital grn and the other is analog. And they should not be grounded together.
Is this correct? I have one going to the black and black ground.

12-25-2008, 02:30 PM
Stickied for easier reference.

05-29-2009, 05:37 PM
'00-'02 Celica GT-S R4 connector: PN 90980-12038

Note: I'm not sure if these are the right pins for our R4 connector, but give your dealer the PN to point him in the right direction and maybe he can tell. Toyota calls them "Terminal, Repair":

Pack of 10 Prewired Female Pins w/6" Pigtails:
Terminal, Repair PN: 82998-12340

Thanks for a very helpful post. If I could update it a bit....

82998-12340 is the replacement part number for the four pins that reside in positions 1, 11, 10 and 20.

82998-12690 is the replacement part number for the other sixteen pins in the connector.

The Wire Harness Repair Manual (RM1022E) is a must have to find every connector and replacement pin. You can search online for this manual or check out this link

08-01-2009, 08:14 AM
I read thru this thread (mostly) to see what this was all about. As an EE, the process/ procedure and reasoning make sense to me and I understand the need for noise cancelation.

But I have never heard of this issue until I came across this post. I have been adding Aftermarket radios for years to my Celicas, MR2 and other vehicles and NEVER have I had this issue.

My last three installs were adding an aftermarket radio to a Premium sound system using the cars OEM amp. In all cases I just bought the adapter, plugged it in as instructed and have NEVER heard any noise.

I'm surprised the issue is as wide spread as the thread would indicate. Maybe I'm just lucky.

I've always bought the adapters from Crutchfield and have never had to modify them to reduce noise. I've done this with two new KENWOOD systems and one old (6+ year old) Sony CD player that had RCA outs.

My last install was on my 03 Celica. What am I missing here?

interesting thread. Thanks.

08-01-2009, 05:07 PM
I understand the need for noise cancellation. It isn't so much noise cancellation (a by-product), as it is impedance & level matching. The standard adapter will drop the input level. But, it does nothing for providing a low impedance termination for the input of the amp and it doesn't account for HU's with different output levels. Without a low impedance termination you have a high impedance input hanging out there, making it subject to acting like an antenna, picking up radiated noise, and amplifying it.

What am I missing here?The $ you paid for an EE that didn't teach you such things.

08-09-2009, 11:48 PM
It isn't so much noise cancellation (a by-product), as it is impedance & level matching. The standard adapter will drop the input level. But, it does nothing for providing a low impedance termination for the input of the amp and it doesn't account for HU's with different output levels. Without a low impedance termination you have a high impedance input hanging out there, making it subject to acting like an antenna, picking up radiated noise, and amplifying it.

The $ you paid for an EE that didn't teach you such things.

If you don't use it, you lose it. I didn't get into the specific field of EE that required me to do much impedance matching.

My comments were based on the fact that many posts are mentioning noise etc. If impeadance doesn't match 100%, I doubt many would even care or notice, unless something like the impedance mismatch is causing and radiating AUDIBLE noise.

I've just never run into this in my dealings with Aftermarket Stereo's and adapter/ harnesses.

08-10-2009, 05:43 AM
If you don't use it, you lose it.I hear ya. ;)unless something like the impedance mismatch is causing and radiating AUDIBLE noise.It picks up radiated noise.
Without a low impedance termination you have a high impedance input hanging out there, making it subject to acting like an antenna, picking up radiated noise, and amplifying it.

08-17-2009, 07:41 AM
Alright quick question guys, I'm a bit confused and can't find a straight forward answer to this one. I just bought my new headunit and I bought the Scosche TA-03B. I am keeping the factory speakers. Will this Scosche TA-03B allow me to still utilize the factory amp to play the speakers instead of the headunit without doing any modification. I understand I may still possibly have all the noise without the above mod. Thanks for your help

08-17-2009, 09:33 AM

08-18-2009, 09:11 PM
just ordered a bestkits harness. According to the calculator I need 500 ohm resistors. The local radioshack carries 470's. Hopefully this will be close enough?

08-19-2009, 06:58 AM

08-19-2009, 04:22 PM
i have a carputer and im getting noise though the speakers, its standard heaphone output for now and soon im switching to surround usb audio but i have a problem also with the backlight of my hvac unit and i can get it to turn on sometimes but than itll go off and im not completely sure on how to hook it up with the harness.

08-19-2009, 05:20 PM
You'll have to provide alot more detail of your problems. Headphone output into? the stock amp?

Backlight problem has many possibilities.... barely broken bulbs, bad flex circuit, power MOSFET in the gauge cluster, loose fuse, etc. etc. etc.

What is it you want to hook up with a harness?

& I'm trying to figure out what your post has to do with this thread? So, please let me know. Otherwise, I'm liable to move it.

09-09-2009, 06:42 PM
are there any harnesses that have the correct resistance in them already and do no need to be modified? as my working time has been cut to weekends at a friends house sine i've moved, the more plug and play the better.

as such, what would you charge to just do the leg-work for me? harness modified to match the stereo and read to just plug in. i have the skills/tools but lack the time/place to do it all. where i work has no internet if something goes awry and i want to look up information...printing this whole thread would be printer death :rofl: PM me if you're interested please.

also, i do electrical troubleshooting/repair at work constantly...its not something i want to come home and do on my free time, understand me?

09-09-2009, 07:26 PM
are there any harnesses that have the correct resistance in them already and do no need to be modified?No. Besides, the resistance depends on the output level of the HU.

its not something i want to come home and do on my free time, understand me? I've felt the same way. Had a stereo that needed a new IC... that sat for years till the ex bought an entertainment center for me to put it in...... and I had to fix it.

I don't do that kind of piece work any longer. So, I won't and can't give you a price. It wouldn't be worth your expense or my time. Current labor rates in my field are $125+/hr.

It isn't that hard of a mod. If you have all the parts together... maybe a 0.5-1 hour with the soldering iron, at most. But, there may be another member that might be willing.

09-09-2009, 07:36 PM
No. Besides, the resistance depends on the output level of the HU.

I've felt the same way. Had a stereo that needed a new IC... that sat for years till the ex bought an entertainment center for me to put it in...... and I had to fix it.

I don't do that kind of piece work any longer. So, I won't and can't give you a price. It wouldn't be worth your expense or my time. Current labor rates in my field are $125+/hr.

It isn't that hard of a mod. If you have all the parts together... maybe a 0.5-1 hour with the soldering iron, at most. But, there may be another member that might be willing.

thanks, i understand where you're coming from as well. can i just ping you for the correct value then, i'm mighty lazy after a week of diagnosis and trouble shooting. evaporative systems are a real annoyance and VW electrical systems are a nightmare.

12-28-2009, 10:30 PM
Thanks for the great post. I may have to go this route, but I would prefer to bypass the factory amp completely. I found a harness that claims to do this, but I am worried about the performance. Should I expect any noise issues by bypassing the amp? Below is the harness I am hoping to use. I may just have to try it and see..

Thanks again.

12-29-2009, 08:05 AM
See the sticky on choices for bypassing the amp.

12-29-2009, 09:25 AM
Thanks. New here, sorry I missed that. Looks like modding is the best option. I'll let you know how it goes.

01-03-2010, 08:49 PM
Great post. Just finished body kit now to replace HU. Thought a piece of cake. Did not use any extra harness & spliced into speaker wires near connector. (did not know about separate amp at the time). Also added subwoofer with amp. Speakers are loud & do not match subwoofer output. There is some noise thou not too bad. If I am successful at this mod u describe will it take care of the signal difference between the speakers & subwoofer and the noise? Hu is JVC KD-AVX11:eek:

02-02-2010, 12:18 PM
Little Confused.....
First of all I've read through this thread twice now and have learned a lot about this mod and so I was hoping to work on it today but I have encountered a problem that has been mentioned several times and I never saw it answered which is that the BHA8113 I received has the original resistors wired right into the harness connecting pins so there's no extended pins. The last person who proposed this same question I noticed 2way told them they needed to read the thread more closely so I re read it before asking but I still haven't figured out what I need to do with mine? Would appreciate any assistance, thanks!

EDIT: OK looks like I've found the information I need with regards to this harness, new Q though?... Are all the BHA8113's now with the series restors wired right into the pins or do some of them still have the extended pins like they were originally reported? Anyone know?

03-15-2010, 01:03 AM
After reading this, i am still unclear to see how much/strong of a resistor do you need any help is appreciated

03-19-2010, 06:11 AM
So dumb question, I looked through the thread but probably overlooked it.
the wire labeled amplifier ground gets grounded where? the other black/white white gets grounded where? I've seen a photo where both wires looked tied together, I've read that both should not be grounded together?

03-20-2010, 08:50 AM
anyone? i've been through the thread a couple times and i'm still not 100% sure. my car is 'over there' and i'm 'over here', walking between here and there in the blustery cold is not fun and there is no way for me to get internet in the car. so i when i do mess with the car, i have everything as close to 100% ready to just 'plug in' as possible. just these last two wires are dangling here...a little help please?

03-25-2010, 06:48 PM
so good news, no sounds, bad news is no sound. common issues that produce no sound with the harness that i should check? powered up headunit here in the home to test its rca outputs, they work fine. help?

03-26-2010, 02:18 PM
POS + remote amp turn on HU lead (or switched +12V) connected to pin 3 of the amp (red wire)?

03-26-2010, 06:19 PM
POS + remote amp turn on HU lead (or switched +12V) connected to pin 3 of the amp (red wire)?

all i have is the harness the fellow made for me, is the turn on for the amp at the radio harness or do i need to go all the way to the amp? which pin/wire at the radio might that be? i want to get this all set and wired to just plug in, my working time is limited and the smoother the better. thankyou.

IDIOT AHOY! i found my problem and thankyou! i totally forgot to connect my striped blue to striped blue. i don't know what i was thinking, i was thinking that was for my basslink which is added later, didn't occur to me that i'd need the remote to kick on the factory amp.

04-24-2010, 07:19 PM
I need help urgently. I am an idiot when it comes to frequency things and i just cant figure out how much resistors i need to put into my harness. I have a KENWOOD KDC-MP342u and this is what is listed in the owners manual.

04-24-2010, 07:35 PM
Use what is recommended for 2V

04-24-2010, 07:41 PM
i looked at the table and it says this:

2v : 154 ohms = 150mv / 211 ohms = 200mv


2v: 154 ohms =150mv / 211 ohms =200mv / 271 ohms =250mv / 633 ohms =500mv / 1.9k =1volt

so i will need 633 ohm resistors?

04-25-2010, 06:21 AM
so i will need 633 ohm resistors? Try 680 ohm.
If it isn't loud enough, go higher (like 698, 715, 732, or 750). If its too noisy, go lower (like 655, 649, 634, 620, or 560).

05-10-2010, 01:29 PM
I have a question here : How do you pull the damn wires out of the connector! I didn't manage to pull them out so I finally decided to strip the RCA cable and put the resistors there... but RCA cables are co-axial (right?) and I only put the resistors on the external wire...I still get the annoying ECU sound.... If someone could tell me how to pull the wires out of the connector or if I had to put the resistors on the internal wire of the RCA...!?!?! Thank you

Edit: I put 330 ohms and my stereo outputs 5v.... They were the only resistors I could find....

05-10-2010, 01:39 PM
I only put the resistors on the external wireNeed to go on the center conductor. The outside is just braided copper shield to ground.

While it will knock the audio level down, to get the best interference reduction, you need to put the resistors you install on the amp side of the existing resistor.

05-10-2010, 09:01 PM
Aight, thanks a lot. I'll need to get it all out once again... :) but that center connector is so thiny... hope I won't make something wrong!! haha

11-10-2010, 06:06 PM
to start, I have a pioneer that is 2.2v @ 1k ohm. and rear rca out only. i used 2 y-adapters to split for front and rear. the wire kit i bought didnt have any resistors in it so i only added 1k ohm resistor to ground for each of the 4 rca wires. it helped the noise, but its still there. do i need to add a resistor inline with my rca cables?

11-10-2010, 06:51 PM
You've got some math and other figuring to do. You will need to decide which series resistance you want to add - the new or the old value - and then do the calculation for 1.1V for the parallel resistor.

11-11-2010, 09:41 AM
well, using one of the calculators list on page 2, it looks like i can wire in 2 matching resistors, we'll say, 1000ohm in-line, and 1000ohm to grd and that will drop the voltage, but 1ohm in-line and 1ohm to ground produce the same voltage drop. the rca out said 2.2v @ 1k ohm. so should i stick w/ the 1k resistors or change all of them? i have electrical in high school, but it wasnt this indepth...
thank you

12-05-2010, 09:49 PM
OP mentioned that if your HU has only 2 RCA pre-amp outputs, you can use splitters but you'll need to double the values of the resistors you solder on. Is that still the case if you mod the Metra/Crutchfield harness that has no built-in resistors to begin with?

12-06-2010, 08:51 PM
Did the mod on the Metra/Crutchfield harness (no built-in resistors) with 500 ohm resistors. My HU had two 2V pre-amp outputs (L&R), and I used Y splitters to hook up to the factory amp's 4 RCA inputs.
Worked like a charm, got rid of 99% noise.

05-08-2011, 08:41 PM
Or ignore all the math, and get you a four channel line out converter, and use the decks speaker level outputs.

06-04-2011, 04:19 PM
Wow, it's hard to believe this post is still going, I think it's been over 8-years but I'm glad it's still helping folks get noiseless sound from their Celi's. And before you ask -yes-, I still have my '02 GT-S and still take it out once in awhile to surf the blacktop because Celi's still drive smoother, faster, and more stable at cruise altitude than most, and the noiseless surround system makes everything outside the windows look way better than a 3D movie ever could (opens moonroof). We love our Celi's.

I'm dropping by to respond to a PM (yes I still get them, though don't always see them right away) and thought I'd share this one. Basically a guy was wiring a radio into a non-FactoryAMP Celi but had noise problems, so here are the cliff notes:

"First, the thread is mainly for those who have the StockAMP and a HU w/LineOUT's to drive it. Find the original thread for pics & help here:

If your Celi didn't come with the optional FactoryAMP, then the Toyota wiring harness is different and your speakers will be wired directly to the Toyota connector from the harness hanging behind the radio.

When you said you didn't connect FR- FL- RR- RL- I'm not sure I understand. The FR- FL- RR- RL- from the Radio -must- be connected to the FR- FL- RR- RL- in the connector from the non-FactoryAMP Toyota harness behind the radio. You can't tie them all together and connect them to ground without risk of creating noise in the audio system.

Usually in car radios w/built-in amps there are 4-amps and each is isolated from the other to prevent crosstalk, including the output wires... they may all be labeled "-" and you may think it's ok to strap them together since they're all labelled the same, but this defeats the purpose of the design which is to isolate audio & noise from each channel from getting back into the other channels.

I think the AMP+ wire from your radio is probably the AMP Turn-On wire which needs to be connected to ACC or IGN (accessory or ignition +12VDC) so when you set your ignition key to ACC or ON the radio will power-up. The non-FactoryAMP Toyota connector/harness doesn't provide this wire, but there should be a single wire behind the radio (color-coded "GR", which I think is Dark GRN w/RED Stripe) and that's the ACC wire for the radio.

If you find it, try connecting your radio's AMP+ to that wire. (If you have a test lamp or meter, test the wire first by putting your key in the ignition and turning it to Accessory to see if it lights the test lamp or shows +12Volts on the test meter)

Once you straighten this out you should be fine."

Good luck,

08-24-2011, 02:07 AM
my car is GTS 2001, have the 6 speakers system with limited wire, only 4+ for speaker no - had the toughest time installing my new system. Recently found an extra harness not connecting to anything behind the radio with 5 black/white wires. I was thinking if that's the - for the speakers until PB confirms it. I don't care its 11 at night im running down to the parking to test it out. Hope it works.

08-25-2011, 11:48 AM
Recently found an extra harness not connecting to anything behind the radio with 5 black/white wires.Sounds like the GND junction connector. Should be a mate on the right side console strut.

01-24-2012, 04:29 PM
Hallo. Sorry for many questions but ..... :-)

1) Is here some possibility to buy some quality brand but notOEM HU which fit Celi 00-02 with JBL directly? Without the mod, noise etc (soldering? may be...) something with the same parameters on the output like OEM AMP?

2) Is somewhere on the net some table with newer Toy HU which fit these "old" cars with factory AMP directly? Something like E7006 with USB etc. Is here some E.Shop with new OEM HU?

3) Are your experiences with the 4resists + 4resists on harness realy so good? I am afraid to buy some relative expensive branded head unit and risk the bad sound.

I was buying some Chinese but not so cheap stereo with the normal sound (tested in RAV4) but if i was connect it with the 4/4 resistor to the amp - the sound is flat.

Thank you for some info! I think that the amp is JBL but probably not :-)

01-25-2012, 09:22 AM
1) The '00-'02 is not JBL. But, does have an outboard amp.

Many folks bypass the amp & replace the speakers. Some have gone the Scion HU route.

However, the sound should not be "flat" if you are using the resistors, the amp, & low level HU outputs.

01-25-2012, 03:51 PM
thanks for reply! I have no idea about Scion (this car is not on EU market) > but as it look :-) > if I understand well > the 00-02 has not the JBL amp - ok. But if I buy some newer Toy / Scion HU with 20PIN output - work this with my TOY AMP directly (plug & play & go) or there must be some other modifications? Is the "later" JBL 20PIN output compatibile with older "NoName" Toyota amplifier and wiring harness?

Sorry for my lame questions but i try read everythink about this but is realy hard for me. If i want Celica i must buy it on Ebay and ship she across the ocean. If i want the simply Scoche adaptor i must buy it on Ebay and waiting about month, if i want some Scion stereo i must buy it on the Ebay and waitng about month, pay taxes+duty+great shipping, if i want ask the Toyota seller in my country he says me "hmm, have no idea, cut the cables"...if i ask the caraudio specialist he says me "You must buy some VW or AUDI, why do you have some strange japanese car?" etc :-) the Europe is land of AUDI, VW and other garbages. IF the peoples are young, they want some small silver VW, if they are older, they want some bigger silver VW, if they ar realy old - the want some biggest silver VW. And Celicas? Few fanatics...

01-26-2012, 07:19 AM
But if I buy some newer Toy / Scion HU with 20PIN output - work this with my TOY AMP directly (plug & play & go) or there must be some other modifications?Should be plug & play.

Is the "later" JBL 20PIN output compatibile with older "NoName" Toyota amplifier and wiring harness? As I recall, yes.

You don't really need the Scosche. Its just convenient. You can cut or tap the existing harness, if necessary.

04-10-2012, 03:33 PM
I really could you some of your guys experiance with my setup as it is a bit unique as the preamp audio source I am using is ~340millivolts @1k. I have read through this mod, and I definitally need to do it, but with my low voltage I am unsure what resistors to use. My TA-03(B) checked out on the meter as having 2.2k resistors, and I know I want as close to 500mv as possible going into the factory amp.

Based on this I assume I should remove the 2.2k resistors as to not lower my input voltage any more, but if I do so what should I use as terminating resistors? I do not know how to tell what size is needed for this low of a input voltage to properly eliminate noise.

Also, is my 340mv close enough to the 500mv recommended for the factory amp, or do I need to use a line driver/preamp to get good sound with the lower input voltage?

Thanks, any inofrmation is appreciated.

04-15-2012, 05:10 PM
Guys, I am still looking for some assistance. My source is a soundcard putting out 334mv with a unknown internal impedance. It is a sound blaster live external USB 24bit. I have tried looking in manual and mfg site to find internal impedance of the card but it doesn't seem to be published anywhere.

I have added a preamp to get the source up to line level, and the preamp brings me up to 4.4 volts so I modded my TA-03b with 300ohm resistors on top of the 2200ohm in it already. The preamp is a Behringer PP400 with a input impedance of 47000 ohms and a output impedance of 50 ohms.

I got all kind of noises in my test in the past few days. Anyone have any suggestions for me? Do I need additional terminating resistors or a change to my setup?

04-18-2012, 12:40 PM
Did you try it straight from the soundcard into the amp?

As for the pre-amp.... output is low impedance.... input is high... you'd probably want terminating resistors on the input side.

01-02-2013, 04:09 AM
Hey PacificBlue, your write up for installing decks with resistors is the best help any could ever get and it is very clear. However I seem to have run into a snag. I have a 2002 gts and I bought the same harness you suggested with the 1.9k ohms resistor and looked at the chart to add another 220 ohms because I believe my preouts are 4v. I followed exactly to your instructions but when it came to plugging everything together I have absolutely no sound. Everything works just no sound. My deck is the pioneer 8400bh. Please if you could tell me where I went wrong I would appreciate it.

Ps I double checked everything. I have just the rca's plugged in,as I didn't connect the speaker wires from the decks harness in anyway.

01-03-2013, 01:52 AM
You might want to double-check if your HU's ANT or AMP ON wire is connected to the AMP ON wire in the Scosche harness (see my last post) Originally this wire activated a motorized antenna when you turned the radio on, retracting it when you turn it off. The Toyota STOCK AMP won't turn on without it. As for your HU's speaker wires, that's right they aren't used... cap or tape them off.

01-06-2013, 12:13 PM
Thank you! for the detailed information PacificBlue appreaciate it! everything is working flawless now and could not be happier with the result, BUT i do have one small problem that came out of no where. when i first got sound, everything was amazing no background noise what so ever but after a few days i noticed a light tapping from the speaks starting. the tapping is only there when the engine is running and doesnt change with revs or load on power (ex. when i turn on highbeams/foglights and move the windows up and down) it also doesnt get louder when i turn up the volume, i can only hear it when the HU is on mute or less than volume 4. Now i havent gone and checked everything yet as i have orderd the microbypass and i am waiting for that to come in before i open everything up again. but other than checking for the obvious like loose connections/ground i was hoping maybe if you had time you could list a couple of things you might believe could be causing the problem.

Ps. im not using the bluebox as you recommended against it and like i was saying the noise was not there to begin with, just recently it started.

And thanks again for your help with your expertice on the matter and for everyone else who had done their testing aswell and brought the info to the table for all to share! YOU GUYS ARE AWESOME!

01-06-2013, 04:25 PM
Glad you're up & running, that feeling when all of a sudden everything works after endless days & frustrating hours is pretty awesome. Welcome back to the quiet world! As for residual noise, you might take a look at the notes on "Troubleshooting Grounds" posted near the beginning of the thread:
Click Here: Troubleshooting Grounds (

For me, adding a heavy-duty copper ground wire physically attached to the HU's metal cabinet and bolting the other end to the Celi's dash frame helped kill-off the remaining residual noise (see link to SWF animatic below pic). Scrape or metal-brush the metal underneath the bolts/screws before you cinch them down. I used crimp lugs on the ends of the wire to protect the copper strands from getting broken when cinching down the bolts: you want all the copper strands you can get. (sidenote: in pro-audio they try not to nick or break the copper strands in the center conductor or braided shield when prepping cables so they get the maximum amount of signal & shielding - the higher the quality of copper & more of it the better)

If you've still got any annoying noises left, you might checkout "Analog Ground vrs. Digital Ground" or in plain English: Signal Ground vrs. Power/Chassis/Frame Ground and why they're kept separate:
Click Here: "Couple more questions... Where does the digital ground go?" (

01-28-2013, 02:33 AM
Thanks PacificBlue your help is as valuable as gold! I got the micro bypass and got everything checked out. I redid the grounding wires as you metioned the pros try not to damage any strands and the background sound has significantly degraded, I can barely tell. I just have one last question. Do you know how many watts the factory amp is kicking? Thanks in advance!

01-28-2013, 05:03 AM
(22) How much power does the OEM Premium Sound amp put out?

The 8 speaker '00-'02 Premium sound amp (6 channels) is supplied by a 15A fuse. Maximum power to the Amp= 15A * 14.4V = 216W.
Now, you usually spec the DC fusing with like a 20% buffer for voltage fluctuations..... so, you're probably looking at an actual max. current draw of 12A (*14.4V=172.8W).

Amps are not 100% efficient. So, say its around 87% efficient (which is probably high)... that puts you at around 150W.... / 6 channels = 25W per channel. More than likely. the amp is less efficient and is rated below 12A (some of that 15A fusing has to go to supplying the HU)... it is more likely around 120W / 6 channels = 20W per channel.

The single rear speakers & the front woofers are rated 25W and the front component mid/tweets are rated 17.5W.

The '03+ JBL system probably has the same max. power. However, it only has 4 channels (no separate sub ch's) and may have a higher per channel rating. If you figure it as a 120W amp, then it would be 30W per ch. vs. the '00-'02 20W per ch.^

02-01-2013, 03:49 AM
Ah, so the factory amp is all used Thank you 2way!

09-13-2015, 05:46 PM
Whats the change the images for this can be hosted here on the forum? None of them work. :wtf2:

Such an informative thread to have to rely on going to another website to read then back and forth to read the posts and comments...

07-29-2016, 03:31 PM
Full article and preserved images on the OP's site here:

04-21-2017, 02:41 AM
Hard to believe I'm posting this 14-yrs after the original post which started the thread. I dropped by mainly to answer a few PM's received recently and decided to update a bunch of dead image links since it looks like people are still finding the thread helpful. And yes, the backup site at Tripod is still up and has all the original images in case the ones here go dark again.

Happy Modding everyone!