Thread: 5V On Ignition Circuit and Car is Going Crazy

Hello all,

My sister has an 04 grand prix GT that has been having some strange issues lately. At first she lost all power inside the vehicle, as in no lights on anything inside the vehicle, no gauges worked, nothing power inside the car except headlights and brake lights. Even the signal lights didnt work. The car would still start and drive. Now when I go to start it, the security light flashes crazy, and the fuel pump and ignition relays are cycling on and off like crazy. I measured the voltage on the ignition circuit when the car is trying to start, and it starts at 5 volts and drops down lower as it goes. Anyone have any clue what could be causing this? It seems to me like its a short in the ignition circuit somewhere. Could it be the ignition switch itself? Not too sure what else to narrow down. Any help is appreciated. Thanks!

Thanks for the quick reply, I will go check that ground out and double check the terminals. I am leaning towards there being a short somewhere in the ignition circuit or the PCM though as all power is fine until its switched to accessory or run.

Ok I checked the grounds on the transmission housing, probably 4 or 5 little ones off of there and they seem fine. I also checked the main ground that goes to the fender area bellow the battery and that seems good. I put the battery on the charger for a while and it will now start at least, but still no gauges or any electronics inside the vehicle. Not too sure where to go next. It does have an aftermarket remote starter, so maybe there's something up with that.

Just an update, changed the ignition switch, but still have no power to the interior. There is no power on the interior fuse block. What powers up the interior fuse block? Thanks.

Thanks, found some electrical diagrams, but leaning towards it being the Body Control Module now.