4x4 on this model is controlled by a module. I will attempt to include wiring schematics:
The module is located in the left rear of the vehicle cab.
Usually, when the transfer case doesn't shift, the problem is with the shift motor.
Also, here is a pinpoint test for you to perform.
There are three wiring harnesses connected to the Electronic Control Module (ECM) :
To check the integrity of these circuits, disconnect the harnesses from the ECM and perform the following checks:EIGHT-WIRE PIGTAIL HARNESS CONNECTOR
FIVE-WIRE PIGTAIL HARNESS CONNECTOR
EIGHT-WIRE HARNESS CONNECTOR