[Vamp]

Granted, I have a Corolla, but the transmission and ECU's should work the same. Anyway, for some reason my speed sensor seems to be freaking out, but only when the transmission is cold. What happens is the speedometer will start shooting up and bouncing around when I'm at a consistant speed, and the transmission will start up and down shifting erratically with it. Once I've driven a few miles though, the problem goes away. Now I have had to add some tranmission fluid to the car because I had a leak. The day I had to add fluid, the speedometer was reading zero for a while (before adding fluid). It fixed itself later that day though. So I added Dex III fluid (recommended for my transmission) and all seemed fine. Then, it started freaking out on me and bouncing up and down, even doing it one morning while I was still in park. Does this 100% sound like the VSS (vehicle speed sensor)? Is it possible it got damaged because I ran low on transmission fluid (stupid torque converter seal leak). If so, know where I can find one for a '01 4 speed auto Corolla?

 

[GSBoek]

If you have a chance, check the connection to the VSS, it could be a lose contact that's playing you like that, maybe the plug is damaged or broken. I have seen this symptom on many cars. I personally don't think the VSS got damaged because of lack of oil.

 

[Vamp]

I unplugged it and sprayed down the connection with electronics parts cleaner as soon as I saw the problem occur. It only happens when the transmission is cold though, which is odd.

 

[1zzfe-man]

Most have 2 sensors one input tubine speed and other is counter gear speed speed sensor.Remove the counter gear speed sensor and look at the end of it.If the end of it is ok replacing it should fix it or have it tested with a scan tool that reads trans codes, ( not all do).

 

[Vamp]

I did get a P0500 code once... when it was reading zero the first time it malfunctioned. It's not throwing codes anymore now. My car only has one sensor on it. I'll take it out and check for damage this weekend. Should it just be a case of remove one bolt and slide it right out?

 

[Jesse IL]

I think its happening when the SENSOR is cold, which probably correlates to the trans being cold. The trans is freaking out because if the ECU has an erratic speed signal, it will cause all sorts of odd shifts.

Not sure the may an auto works, but on a manual the VSS feeds directly into the gauge cluster, and the gauge cluster back-feeds the speed signal to the ECU. There is a test in the SFI section of the service manual for the VSS. I'd check that out.

 

[Vamp]

I have a copy of the test section of the service manual. It basically has you test the voltage, which appears correct unless the problem is occuring, which is not all the time. It's off and on. It's going to have to be a weekend project to look over this, since the VSS is a pain in the ass to get to on my car. What are the chances that it might be something more than just the sensor, in terms of the transmission itself? Granted, I've had no noticable issues with the transmission when the sensor it working properly.

 

[gameboi]

why not just let the car warm up then drive?

 

[Vamp]

I had a separate speedometer hooked up to it, and it read the same as the gauge cluster. I'm going to check the harness to make sure it hasn't suffered corrosion that I might not be able to see upon quick inspection.

gameboi, I have to drive the car for a few mile to warm up the transmission. A real pain when it's wet out like today. Even worst when I'm in boost.

 

[2way]

What Jesse said is correct. If the speedo is freaking out, too.. then the problem is most likely between the gauge cluster & the VSS (or the VSS is bad). Providing that you don't have a problem with the tranny itself... a clutch, brake, or gear.... that is causing the output shaft not to rotate... or busted teeth on the sensor's driven gear. Have you pulled the VSS & examined it?

I had a separate speedometer hooked up to it,

Depending on where you had that hooked up... it might have caused damage to the connection.

 

[Vamp]

I have my Greddy Autotimer hooked up to the ECU, but I've had that on there for 3 years now (soldered connections), so I don't know why that would cause issues all of a sudden. It also reads the correct RPMs the entire time, which comes off the same wire. I just tried to take the sensor out, but being that I don't have that long of a lunch break at work and it's going to require the removal of some other parts in the way to get to, it'll have to wait until tomorrow. Now I've seen some pictures replacement speed sensors for my car, and they didn't have any gears on them, but some of the older ones I've seen do. Is the gear part of the sensor? Or is it only on older transmissions that have the gear?

 

[2way]

I have my Greddy Autotimer hooked up to the ECU, but I've had that on there for 3 years now (soldered connections), so I don't know why that would cause issues all of a sudden.

If it's tapped @ the ECU... it's after the gauge cluster.... so, it shouldn't cause the speedo to go nuts. Can't help you with your gear question, tho.

 

[Red Pyramid]

It sounds like your having the same problem I did on my auto GT. The tranny would up shift and down shift like it has a mind of it's own. And the speedo would bounce around. Toyota kept telling me it was my speed sensor. Over the last 4 months, I've went through 3 speed sensors. The problem kept comming back, But here lately everything's fine...or so I hope :ugh:

 

[Jesse IL]

What are the chances that it might be something more than just the sensor, in terms of the transmission itself? Granted, I've had no noticable issues with the transmission when the sensor it working properly.

Basically impossible for anything to be wrong with the transmission. The VSS is a mechanical device. The differential has a plastic gear on it. The VSS is two parts, the sender unit and the driven gear that is run off the differential drive gear. The VSS has three wires: power, ground and signal. It gets power, has a ground, and the turning of the driven gear causes it to send a square wave signal. Think of it like a mini alternator almost. You could have a ground issue, as those for some reason seem to be more apparent when its cold. So the sender in the VSS is being physically turned to the transmission and sends a square wave to the gauge cluster, which interprets it and drives the speedometer. The gauge cluster then back feeds the speed signal to the ECU, which controls the transmission.

There's another option but I don't recommend doing this except as a last resort. You can run the whole system off the ABS ECU (assuming your car has ABS). I had to do this on my car since my Cusco diff has no spot for the speedometer drive gear. It turns out that on a Spyder, the speedometer is run by the ABS ECU, not a VSS (there is no VSS on that car). The Celica and Spyder ABS systems are made by the same manufacturer, although the Celica system is more advanced. Both systems have identical plugs, and there is a speed signal generated on the same pin in the Celica, but there just isn't a wire hooked up to it. What I had to do is get a new pin from Toyota (what they call a wiring harness repair kit). This is a pin specific to the connector with a length of wire attached to it. There is a number molded into the connector and you need to have that number in order to get the right pin. I then simply inserted the pin into the connector and ran a length of wie to the VSS wire going to the gauge cluster, cut that and spliced in the new wire coming from the ABS ECU.