My 01 Yukon was running great until after I left it at my sister's house while moving, I had a Camper I needed to tow with my truck before I could retrieve the Yukon. I just remembered they said the battery died in it and they jumped it to move it. I know my sister didn't but my brother in law who I don't think is very bright because he almost burned her house down . If he connected the jumper cables backwards could it have caused the Fog lights, Cruise Control and Door ajar to stop working? I've been looking for chewed wires , broken ground straps, blown fuses and bad relays , everything seem fine. The Fog light relay has power and works. When I check the voltage at the fog light bulbs one gives me a low voltage 9-10v the other nothing? The battery is at 13.5v. Could the ECM have been damaged? My code reader doesn't seem anything different than normal. I'm completely lost at this point what to look at the Yukon is/was in perfect condition for its age until I left it in the care of someone else. I don't have any proof he reversed the Cables he's not the kind of person to admit fault any help how to figure this out. It's really ruined it's sale value.