1989 Lebaron runs intermittently?

I have a nice 1989 Chrysler Lebaron that the speedometer goes haywire on, it bounces all over the scale then quits. I can't use the cruise, and sometimes the engine shuts itself off after about thirty miles of driving or less. The code says something about secondary power to the computer being lost?? I would like to find a wiring diagram for this critter. Is the speedometer electronic?? thanks