Transmission & Temp sensor questions

[Liz73]

Well, I took my car to the "Transmission Guy" and was told that it would cost $2,944 for a transmission overhaul and $40 for a temp sensor replacement.

Now, I may be blonde, but with a trasmission overhaul they don't replace the transmission, do they? Basically all I'm paying for is labor, right? If that's the case, he's pretty much trying to screw me, huh?

As for the temp sensor, when the check engine light came on in my car before, I took it to Auto Zone and had them hook it up to the computer and get the code. They said it needed a new temp sensor and gave me the part I needed (or so I thought). My brother-in-law replaced it, but the light didn't go off.

The transmission guy said that there are 3 temp sensors, and that the wrong one was replaced. He said I need to replace the computer temp sensor. I'm curious to know if there are indeed 3 different temp sensors or if he's just full of it trying to get more money out of me. Any input would be appreciated. Thanks in advance!

[muff34]

Blond eh.......hmmmmm . Opps get back on track............lol. find a new "transmission Guy" .What is the problem with your transmission?

[Liz73]

I took this from my previous post:

I have a automatic 98 Cavalier which has given me no real problems up until now. Lately, my car's been slow to accelerate and it "shudders" when shifting gears. It gets so bad that it will make the car jerk. NAPA suggested adding Shutterguard to my transmission fluid, which I did and it was ok for a day, then back to jerking. I brought it to my mechanic last month and he changed my transmission fuel and filter and said it should be fine. NOPE! Not even a little better. I'm just wondering if I need a whole new transmission or if maybe there's a less expensive solution.

So that's why I took it to the transmission guy. He also said something about the transmission shifting hard because it's cold (my temp gauge is stuck on C). I'm hoping maybe once the temp sensor is replaced, that will fix the problem??

[Blue Bowtie]

A '98 should have a coolant temperature sensor which serves the PCM (computer) and is used for cooling fan, transmission, and fuel mixture control. There si also a temperature sensor in the transmission, but that was apparently not your trouble code. The sensor you need to find should have a yellow and orange or orange/black wire connected to it.

What was the specific trouble code? There is a code for a shorted/high temperature reading, another code for an open/low temperature reading, another for sensor performance, and possibly another for intermittent sensor signal. Replacing the sensor may have been a waste of time of the electrical connection(s) was not intact. Having an incorrect CTS input can cause various problems, not the least of which is poor fuel mileage, late shifts, hard starting a warm engine, etcetera.

[Liz73]

These are the codes that came up:

PO118 - Coolant Temp Circuit Signal High
PO705 - Transmission Range Sensor Circuit
PO742 - TCC Circuit Stuck On

I'm thinking that once I fix these codes I won't need to do anything to the transmission. (Hopefully!)

[Blue Bowtie]

The P0118 indicates an unreasonably high signal in the CTS circuit (no pull-down resistance from the sensor). This occurs when the CTS fails in an open circuit mode, or the CTS is disconnected, or the circuit between the CTS and PCM is open.

The transmission range switch is mounted to the outside of the transmission, on the top of the transaxle at the left rear corner:

The transaxle main electrical connector is at the front of the transaxle. These connectors in earlier models had a tendency to work loose, and there was a modification to add latches in later revisions to prevent this. You should be able to see it here (image courtesy of BNaylor):



Given that multiple transmission codes exist, this connector is suspect. If the connections are not reliable, the PCM will revert to a default shift mode, forcing full (unmodulated) line pressure and may inhibit the TCC function as a safety measure. This would result in the harsh shifting you describe. These circuits also connect to the PCM, so it may be beneficial to check the connections at the PCM for ALL of your problems.

The PCM on your vehicle should be located at the extreme right front corner of the vehicle, above and behind the RF wheel splash guard. It can be removed by sliding it downward from its mounting bracket. The electrical connectors can be removed and inspected for corrosion, damage, and moisture.

Once the problems are resolved, be certain that you drain the transmission, change the filter, and refill it with clean ATF. You'll want to get that shift/friction modifier OUT of the transmission as soon as possible.

[Liz73]

Blue Bowtie, you're the best! Thank you sooo much! I'll give this info to my brother-in-law and see if he can take care of it.