Remove your passenger side headlight to gain access to your front axle actuator. Itès loacted under the battery tray and itès like a brake boost, just not so big.
Inspect it for any signs of damage and also inspect the vacuum line that itès connected to it. Have someone push the 4wd button and see if the actuator is pulling on the actuator cable or not. If the cable is not moving, than you have a vacuum issue or the actuator has a rip on the diaphram.
If the actuator move the cable, then inspect the cable to make sure itès not broken off the front axle at the pumpken. (Differental)
Replace any parts that is damaged and keep us posted.
