It's been 2 years since I had what I recall is a similiar problem. The outcome was a corroded splice. I have a 98 but I'm guessing they are the same. One of the things that finally led me up to the splice was the door unlock on the drivers side of the vehicle just inside the rear hatch. When I used that switch to unlock the doors they all worked fine. The splice I had problems with is located under the "sill", for lack of better terms, at the drivers side rear door. It's the piece your foot would step on if you were a little kid climbing into the rear driver side door. The wires are white/pink and if I recall correctly there are 4 of them spliced together and covered by a factory heat shrink. They get corroded and lose connection. Let me know how you make out.
