I bought a 07 g6 went to use the aftermarket connector had it wired up the guy before did something weird the wires. My dad and I were trying to find the positive in the mess it touched the metal did the same thingI got my Kenwood radio from Crutchfield and also bought the little box that's used to properly terminate the factory DIC wiring. Not sure how you wired up your radio but I would suspect that is the problem. I don't think leaving wires simply dangling is a good thing with these cars.
did you ever find out what to do? I bought a g6 the previous owner did something weird to the wires they were tangled and a mess. Tried sorting them out positive touched the metal my headlights and horn work nothing else works. Do you have any advice?Did you ever figure out the issue?
I'm dealing with the same issue in my 07 g6 after attempting to replace the radio