I have a 2002 Chevy Impala, 3.4 L engine, auto trans. You start it up and let it idle in park and all is well. When you move the gear shift lever the AC shuts off and the cooling fans shut off, and they will not restart until you put it back in park shut off the engine and restart the car. The cooling fans and AC will then work normally until you move the gearshift lever again, then they stop. This only happens when the engine is warm, if you start it cold you can drive off and everything is fine until the engine gets warm and the AC will shut off and the cooling fans shut off. I've checked with everybody and their uncle, including two chevy dealers and no-one has ever heard of this before. Can anyone Help??? I've changed every sensor I could find that might fix it but so far nothing works.

 

It may be the PCM/BCM (powertrain and body control module(s)). That is the only thing I could think of.

 

Racking my brain on that one and trying to picture the relationship between engine temp, gearshift position, the ac, and cooling fans. What "Hot" said is about the best I could come up with either.

I'll try running the scenario past my favorite GM guru as soon as I see him, so check back. Maybe someone else has seen it and will post. That's a weird one.

Just curious, but was one of the sensors you replaced the coolant temp sensor (the one for the PCM, not the one for the temp gauge/light on instrument panel)?