Odd indeed. I will be very interested in hearing what the problem is.

the only thing that hasn't been tested thoroughly is the pcm. thats the only other thing i can think of, but since nobody has seen a bad pcm on a gxp, it makes me wonder........

SUX. I had a LaCrosse with a cracked chip in the PCM. Anythings possible. But it diagnosed itself. It was then I traded up to the BonnevilleGXP. Always sux to take a car in w/ a problem like this to the Stealership out of warranty, no doubt.

Just because we have not seen it, doesn't mean it can't happen. The GXP is a newer car with less history to go on. As I said, there is a list of possible causes, start with that list and test the easy first, scratch off each item you test/check, and your left with the cause.