My father in law had a similar problem this week with his 2001 RAM 1500. His ABS, Air Bag, and BUS warning lights were staying on. Meanwhile, he had no running lights, power windows, or heater; and the speedometer wasn't working.
Other than this, the truck ran fine. Yesterday, he and our local mechanic figured out that there was a loose connection (a wire had come unclipped) in the steering column, probably due to the fact that my father in law adjusts the angle of the steering column every time he gets in or out of the truck. Apparently, the wires in the steering column were bound quite tightly together, and there was not enough play for repeated vertical adjustment of the steering column.
The repair cost $60 cdn. and a case of beer.