I've got a question that I hope someone has some clues about, because we're stumped. I've got an '09 Cobalt and when I give it gas (from a stop), the car loses power immediately, the check engine light and the traction light both come on, the read-out says to "service traction" at first, then switches to "engine power reduced" and it becomes more gutless than a smartcar. My bf is a mechanic for a shop, and even the head diagnostic guy is confused on this one. I purchased the car used in 2011 and this is the first big problem I'm having. My bf got in there and found out that the computer was totally loose and had been bouncing around in there for the three years I've owned it, and thought that could have been the cause of the problem. He put it in properly (visual inspection showed no damage to the computer component) cleared the code (which is consistently p0641), and it was fine for a week, and it did it again. He got the head guy to take a look after he looked again, but they're both stumped, because it appears to be fine until it has this problem. It just did it again today about a month later (and 8 days after my warranty expired naturally), and we're still stumped. Any info from anyone who has seen this before would be greatly appreciated. It doesn't appear to be something that will strand me somewhere, but we're all a little confused now. The only common factor so far that we've noticed is that it does it right when I push the gas pedal from a stop or a very slow speed, and it's not like I'm putting the pedal to the metal, either.

 

Have you disconnected the battery? Any mods?

 

Your PCM is bad. The PCM generates the 5 volt reference signal used all over the car.

Also note that the same 5v signal is used for the wireless throttle si when you put your foot into the gas it drops the signal.

Test this by measuring any point on the car that uses 5 volts which is any sensor. remember to have the car running so you can see the drop.

Also note that the throttle at your foot or on the throttle body could be bad and shorting out the 5 volt signal.(this may be the likely candidate.)

 

Must not be too important to figure out as this is their only post and hasn't been on since.

 

or they sold it lol

 

I had the same sort of issue with my 07 and it turned out to be the throttle body.................