PCM Questions and Problems

I am currently having the same problems as you with my 2002 Alero. The milage is just over 204,000 and the engine light is on. I took it into a GM dealership to have a buddy look at it and he said the PCM is fried for the temperature sensor. I will have to replace the whole PCM as you cannot just change the wire. The PCM costs around $375 and 1 hour labour.
Also I am having problems with the trany.....it clunks when I put it into drive and when I am shifting thru gears. My mechanic said that this is either the pressure control solenoid being wide open in the trany or maybe has something to do with the PCM. If you come across any info on these problems let me know. I just bought the car 6 months ago and all of a sudden everything is going wrong! Thanks!!

Due to the age of the original thread you posted at I have moved your post to a new thread.

The PCM module controls shifting and line pressure so I would not rule it out. Also, another cause of hard shifting could be the IAT sensor at the air intake if you have a 3400 SFI engine.

You should be able to get a used PCM module like on Ebay cheaper around $100 and less. It must match your year and engine size. Also, a local salvage yard.

Thanks!! If there was a problem with the IAT sensor would it show up on a diagnostic?? My mechanic ran it thru the computer to see why the engine light was on and came up with the PCM issue. My car is a 3400 engine.
I will take a look for a used PCM.....it would be much better than paying $375!!!

Not necessarily. But since your PCM ECT (temperature) circuits are supposedly not working it would be a moot issue. I would get the PCM replaced.

There is a GM TSB out on the IAT sensor causing hard rough shifting when going into reverse or drive and abnormal shifting so that is why I mentioned it. A few of our members had a problem with it too.