Chevrolet Repair Questions? Ask a Mechanic for Answers ASAP
A few things that might help you solve your issue:
Having clarified those points, what is the issue you're trying to diagnose? Batteries going dead overnight? Not enough electrical power to start the engine? "Battery" icon lit up on the dash?
I'll be back online tomorrow after 2PM ET. I look forward to hearing from you then.
Now I see how you could have gotten confused. This issue has to do with the 5 volt reference signal the onboard computer sends to several sensors. If the onboard computer detects a sensor is shorted to ground, it will set P0642.
A scan tool such as the Tech-II, capable of reading sensor data, can quickly show you which sensor or circuit is causing the issue. Not having that kind of scan tool available makes diagnosing this issue the same as cutting down a 100 ft tree with a kitchen knife; very hard. You will have to check voltage with a voltmeter at every individual sensor until you find the guilty one - sensors to check are cam, crank, intake air flow valve, fuel tank level sensor 2 and EV fan sensor.
Please tell me how you want to proceed and how I can help.