Should I try replacing my PCM?

**50Coupe** · 11-23-2011

I have a 2000 GTP. I'm having a little issue with my rebuilt trans finding first gear sometimes. The guy who rebuilt the transmission told me the pcm in the car isn't the one that came in the car. They tried to reprogram the pcm to stock, but I'm not sure it worked - (it was at a GM dealership though). I'd like to try replacing it with a stock pcm in an attempt to fix the shifting. I'd rather spend $100 trying something than to give it back to him and have him chase a ghost.
I'm getting sick of this transmission situation, since I spent $1,200 to have it rebuilt.

**Trannyman95** · 11-23-2011

You could try a different pcm but I doubt that is going to fix anything unless you are throwing driver and shift solenoid electrical codes and it is not commanding the solenoids as they should be. There are a few things inside the transmission that can cause a 2nd gear start either cold or after being warmed up. Also- I have ran into bad new aftermarket shift solenoids that once warmed up caused the car to want to start off in 4th gear after driving in D range for a while and work fine once cooled back down. The shift solenoid output function of the pcm is simple and if there is any electrical fault there should be a code, doesnt matter if it is the correct pcm for your car and you could use a 98-02 GTP pcm and it will work fine. If there is a gear ratio problem it would throw an incorrect gear ratio code, especially if the pcm was just reflashed back to stock at the dealer. Have you tried to manually shift the car back into 1st when this happens to see if it works ok or does that not help any?

**50Coupe** · 11-24-2011

Thanks for the help. I had the transmission rebuilt by a certified GM rebuilder, I'm trying to trust him and give him the benefit of the doubt - especially if something else is causing my issue.
What happens exactly is when you backward out of the driveway or go to take off from a stop, the engine will rev a bit before the transmission will engage. It's enough to drive you crazy, especially since I just spent $1,200 having it rebuilt. I probably need to leave it with the rebuilder again, but trying a $20 stock junkyard pcm would be easier if it's a possible fix. Would a 2000 gt pcm work in a gtp?

**Trannyman95** · 11-27-2011

Ok, sounds like you have an input clutch problem then and here is a link to our website that has some detail on it and is a pretty common problem

No Forward Cold

Not many people ever look at the input clutch piston or even take it out of the drum during a rebuild. Seals can also be easily damaged during a rebuild and cause input clutch fluid pressure to bleed off and cause a slow apply. Any significant pressure leak anywhere in the trans can cause this also