Would someone who knows be so good as to explain where all (or as many as you know/are willing to explain) the main electrical grounds are on a 2000 GP GTP? I've got a bunch of accessories that all went out at once, and that's what I'm betting on. BTW: Checked the fuses (even under the hood) -- all good.
I have an Alldata subscription, but am no good at reading electrical diagrams.
If it helps, the accessories not working are: daytime running lights, power locks (though the relay under the dash clicks), radio (every aspect of it), lumbar adjustment, rear window defogger, and seat heater.
Everything else works fine, though I've had the infamous "rainwater onder the passenger floorboard" issue many times over (any grounds under there? My blower motor actually has rust on it). Auto AC is fine, as well as auto headlights, signal, parking, and dash lights, HUD, power seat, DIC, dome light, brake/backup lights, engine starting (still instantaneously after 5 years and 135000 miles, in fact) -- you name it.
Since all the accessories failed at once, simple logic says they must have a common problem, and I'm betting on a ground. If it helps, I first noticed one day when putting the car into park that the radio woud be "pulled down" (the display would temporarily fade), and it would turn off when shifting into park. This, I discovered, was due to the factory computer setup of auto-unlocking the doors when putting the gear selector into park. I disabled that and the problem went away, but the radio still continued to be a problem when going over bumps. The display and sound would dim, then return, then dim -- and finally faded away altogether. Also, the power locks tried to actuate (when I pressed the button or set the alarm), but seemed to lack sufficient power to trip completely. DRL faded away as well.
This originally happed in the summer of 2004. Last winter, on the coldest days, the radio display would return dimly, but no radio sound. Some current was still going to the radio, obviously, because the time was still correct, and the station buttons still held the correct frequencies. Also, the lumbar adjustment began working -- but only for a minute, then dead again (after warming up?). No such joy this winter, even with equivelent temps.
I've really got the feeling that this is something fairly simple -- a ground -- but finding it without any idea of where to look would be a fool's errand. So, again, can anyone point out WHERE and and all grounds are? In addition, what do they look like? I'm assuming a bunch of wires come together to a bolt, but will this always be at some otherwise blank spot, or might some grounds be located on an actual component -- like the blower motor? Any other ideas would be appreciated as well.