2007 Impala 3.5L P0641

Posting this for to help anyone out there that runs into this code, which will usually be accompanied by the car going into limp mode with a ENGINE POWER REDUCED message coming up.

There is a service bulletin (PIC 4610A) concerning this issue which basically states that you check for wire chaffing in three areas:


Where the wire harness passes by the power steering pulley
Where wire harness passes over over the transmission housing
Under the rear seat on right hand side


We found our chaff point by the power steering pulley area. Verified it by attaching my scope to the 5 volt reference at the MAP sensor and then used a wire attached to battery negative and touched the exposed section of wire. It pulled the 5 volt reference to ground. We had had the car in a week earlier with same symptoms but missed this spot (hadn't located this service bulletin) and at that time could not reproduce the issue by wiggling harnesses while monitoring the reference voltage.

It took driving conditions for a bump in the road to tap that exposed wire onto a ground point to send the car in limp mode (don't take much..lol)

Hope this helps others. BTW you could probably monitor that reference voltage with a decent DVOM and not need a scope.