03 silverado 2500hd tranny problems
 

Heya,

I have a service 4wd message displayed and am trying to figure out the issue. I have an actron cp9580 scanner and the only code it brought up was for a random misfire (intake manifold gasket i think). I assumed that a 4wd selector switch or encoder motor/transfer case issue would set a check engine light but maybe that is not the case. I have the 3 button 4wd selector switch in the dash (no auto) and cannot select 4wd. The lights next to the switch light up when i turn the key but are not illuminated after that. I have checked all fuses and they are fine unless the encoder motor has it's own fuse. I have over 150,000 miles on it and have to admit that i haven't been good about changing diff fluid or cycling 4wd in off season. Any thoughts of where to go from here as opposed to replacing components randomely or taking it to a dealer and pay $100 for a scan since i spent $200 on the one i have? Thanks.

well I would say it is probably a service reminder light based on mileage.......if it doesnt show with a scan and you are scanning the power train part then its related to mileage I would say.

It's more than a service reminder, i cannot switch into 4wd. I assumed that a faulty 4wd selector switch in dash or encoder motor would set a check engine light but it doesn't appear to do so.