I had a 2000 Olds Silhouette which was its sister van. It was a lemon and I actually won on a lemon law suit. The problem: the the alternator was never ground properly. Defect in design. There was even a recall on this issue. I brought the van in so many times for the same problem. It was only fixed after, on the advice of my attorney, I brought it into another dealer. To fix the problem, there was a part they put in to ground it properly. My guess is this is your problem.
