my 4wd light wasn't working either, the full time and part time were both out. The guy at the dealership first told me the bulb was burnt out, but I had to take it in for other reasons and I asked them to check the light out for me too since it's still under warranty. Anyway, they said the switch was bad...Doesn't make sense to me because I was still able to go into 4 high and low, but that's what they told me, and it was working when I picked it up. So I would say check your switch.
2000 SE. 2" ProComp Lift, 32"x11.5" MTR's, AirRaid intake, Hesco throttle body spacer, JET Stage 1 Chip, Redline Performance Chip, a couple of KC's.