'04 Z-71. So driving in to work yesterday my info center suddenly said "service 4WD." I haven't used my 4WD since last winter. I tried to put it in 4 and no go. Won't go in 4 or Auto either. Any ideas??? is this just a factory installed setting to get you to take it back to the dealer for some BS service thing they can over charge you for??? Oh yea, it has a little over 64k miles on it.

 

When I had a problem with mine it was the switch in the dash, think I've heard of actuators going bad also...

 

you need to find out what code it has in it.... If it is a C0327, you will need an encoder motor sensor. SOMETIMES, the seal that keeps fluid out of the encoder motor will leak fluid in to it and make the sensor short out. I have replaced lots of sensors and now I am starting to have them come back due to the fluid leak inside the encoder motor

 

Put the truck in neutral, and see if you can put the transfercase in neutral with the button, then try to put it in 2wd. Mine did it once too.

 

If it doesn't do anything when you push the button, it's probably the switch. If you push one of the buttons, and it flashes that button(flashing light next to 4 hi for examp) it's probably the encoder motor, or the front actuator.