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7 Posts
Discussion Starter #1
How we doin boys, hoping someone can help me out here,

My OBD2 scanner won't connect to the ECU, I've spent the last two weeks trouble shooting and I'm fairly certain my OBD2 connector is wired wrong. Before I continue let me just say:

  • Every fuse is fine. EVERY FUSE. I've used test light, continuity on multi-meter and visually inspected EVERY fuse and relay in the engine bay and under the steering wheel area, trust me.
  • It's not a PowerFC or aftermarket ECU, checked all that.
  • Scanner works on both of my Dad's cars, so scanner is fine.
  • Car runs and drives but something feels off (according to my Dad), hence trying to obtain some error codes
  • Got 12 volts on pin 16 and ground on pin 4 of OBD2 connector so power is getting to the scanner, HOWEVER pin 5 is missing and it looks like the a few of the other pins are in the wrong places.

From what I've researched there are a few protocols going on in this plug, ISO 9141, 15765 and whatnot, but none of my pins are paired like they should be, I'll try and attach an image of what it should look like and what mine looks like.

Thanks to anyone who can help, I included the wire colours in my diagram with question marks as I'm not sure what they are yet or if they're even the standard colours (some of the wiring in this car looks sub-standard so not surprised if the previous owner just used what they had laying around).

My car is a year 2000 Celica GTS with a 2zz-ge, 6 speed manual if that helps.

Here's the standard connector

Here's my connector

161 Posts
What kind of ‘off’ is he feeling?
Do you have a CEL light?
what have you OR HE been playing with?
has he ever driven one of these to judge?

7 Posts
Discussion Starter #3
I replaced the timing chain cover gasket and when we started the car it was idling low and would sometimes stall, he's worried that I may have messed the timing but I don't think that's it
The car runs alright but when you accelerate it kind of sputters for a second then idles ok, like a sneeze really, honestly I'm not sure if it's anything too severe I just wanna be able to read some error codes and confirm anything is wrong.

My dad has not owned a 7th gen but he had a 4th/5th gen back when he was young so not really helpful there, but he does have many years of car experience so if he says something doesn't sound right then it's probably worth listening

Have you ever read your error codes or at least know a mechanic who's been able to?
Do I need a special Toyota-specific reader or is there no hope?
Thanks for replying btw g

121 Posts
That sounds like the IAC valve. Idles really low, and when put in gear will sputter and sometimes die straight out.... You can try the throttle body cleaner, if that doesn't work, you will have to pull the throttle body split it and clean it that way. Just make sure you buy a gasket, otherwise it wont seal properly and it will be sucking up coolant causing a misfire, or multiple misfires..

7 Posts
Discussion Starter #5
Thanks for replying Blackdemon, I removed the throttle body and IACV and cleaned both of them rigorously just last week, replaced both gaskets too, even cleaned the PCV, still nothing.
When I did the timing chain cover gasket a few weeks back I replaced the lift bolts, the thermostat (just coz), the chain tensioner and it's got all new coils and spark plugs and MAF sensor, as well as a new air intake filter so at this point I'd rather get a specific code rather than throwing more money at it.

I read somewhere that Australian Celica's didn't have OBD2 compatibility until 2005 or something so I guess I won't be able to read anything unless I take it to Toyota? Maybe they have a proprietary reader? I'm really not sure but I am definitely not giving up hope, I love this car and just want it to run like a dream again

I'll keep you guys updated, maybe I'm helping someone in the future

32 Posts
Ok so here is the deal. When you removed the timing chain tensioner something rotated and the lock pin in the intake cam advance sprocket got locked in place, the ecu can no longer control the cam timing.
When you reinstalled the lift bolts they went into the wrong hole.
Way more likely that when the tensioner was removed a valve spring rolled the cam to a neutral position and locked the cam timing sprocket. The bolts have 5 flats. Take one out and get Allen head bolts to replace them all. Now you can remove the cover plate and manually unlock the pin and rotate the sprocket.
There are online instructions to use air to unlock it while you rotate it but it is less trouble for me to just replace the bolts so I can access the mechanism by hand.

I dont know what could be your obd2 problem.
Hope this helps.

Electromagnetic Wave :-h
15,508 Posts
If this is the early JDM style, you connect pin 4 to pin 13 with the key OFF. Turn the key ON & codes will be flashed by the CEL.

Trouble code.  
no problem​
air-flow sensor​
intake air temp sensor​
water temp sensor​
throttle position sensor​
O2 sensor​
fuel too lean​
fuel too rich​
knock sensor​
crank position sensor​
cam position sensor​
speed sensor​
ISCV system​
ECU abnormality​
trouble in ignition​
VVT sensor/function​
multi-signal function​

the lock pin in the intake cam advance sprocket got locked in place,
The VVT pin locks when you turn off the engine (loss of oil pressure).
Australian Celica's didn't have OBD2 compatibility until 2005
2003+ are.

Did you disconnect the battery at some point?
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