there si one ground in the rear in the back passanger corner (IIRC) just pull the panles and trim out and follow the wire harness, up front I can'tremember which side the ground is on, but I believe it's on a rame rail (IIRC) sorry but so many car I have a ahrd time remembering the details on each
the easiest thing to do is to locate the ground wire leading to the non functioning light and run a good new ground to it, if this fixes the problem then youfound the problem, if it blows a fuse you hooked to the positive
has anythign changed lately? a lot of times people put in aftermarket stereo's and groudn to the illumination circuit causing all sorts of drama