Thanks for your reply. My car does three things intermittently: 1. It will start and run great with no code set, 2. It will crank but not start and 15 min later crank right up or 3. Be OK until moving the key to "start" position where everything goes dead (no dome light, headlights or dash lights) until the key is out of start, than everything comes back on. #3 is where the mechanic shows a dead short with the load tester. I've had 4 new batteries this week, and both battery cables have been removed and cleaned.
My mechanic is baffled, and I will pass along your suggestions. Thanks again for your replies. This forum is a lifesaver!