What does the instrument cluster show for battery voltage while the car is both running and not running with the ignition on?
Do you have wiring diagrams for the car?
Your problems are wide spread enough that I'm not convinced your problem is a bad ground (unless it'* where the battery cable bolts to the body). Have you thoroughly checked your battery cables for corrosion. Often these can "look" okay, but pulling back the boots has frequently revealed problems. I think in this case, this should really be your first check.
Here'* the problem... Each door has its own door control module to manage all functions within their respective doors. All door control modules communicate using a data bus. The problem with the "ground" theory is that each of these door modules all ground at different locations in the vehicle. For all doors to quit at once would be so extremely coincidental that I can't even imagine the math to figure out the probability. Additionally, you have other issues going on and again, these componenents also ground in different locations. What you're describing sounds more like a general "voltage supply" problem than an individual component or module ground point.
It is very common for people to jump on a "bad ground" with these cars, but this is seldom the case in the 2K+ generation. Not so uncommon in pre-2K however. Grounds in the newer cars are a better design and located in places to avoid the moisture that plagued pre-2K cars ground busses.
StingRay Bike w/cards in the spokes, Weeeeeee!
Last edited by ddalder; 02-18-2009 at 02:40 PM.