2002 envoy has the service 4wd soon light. this is an intermittant problem. seems to only be a problem when the car is left out in the cold. for over 8 hours. no lights on the switch in the dash when service light is on. is this a switch problem or a module problem. if module, where is it located.

thanks,
mark

Bump for you

How many miles do you have? Not sure I understand this part "no lights on the switch in the dash when service light is on"

If it's only doing it when cold, it could be a few things.

1. Fluid is low
2. Filter needs changed
3. Line pressure problem

Sending you a PM.

there are led lights on the switch showing what mode you have selected (2 HI, AUTO 4W, 4 HI, 4 LO). when the service 4wd light (not service engine soon light) comes on the instrument panel, the led lights on the switch are not lit. there are 77,000 miles on it

Oh, I see. Does the LED go out even in 2WD? Just curious.

Check your private messages.

yes, when the service light comes on the instrument panel, all led lights are out on the selector switch.

had to replace the transfer case control mod and then have it reprogrammed.

ahh this happened to my sierra I just ignored it and when I went in to get the circut board for my windshield wipers repaired it fixed this problem. I dono if it's the same deal for the Envoy as the sierra. I would listen to Obsessed since he own's a trailblazer.