When transfer case is in AWD mode the transfer case control module monitors the front wheel speeds and the rear wheel speeds. When a noticeable difference between the front and rear is seen the transfer case control module sends a PWM voltage to the clutch coil so it can apply the clutch in order to correct a slip condition. The slip condition is the difference in speed between the front and rear axles. The module has a thermal model based system so when the slip correction can not be made when a high percentage PWM signal has been sent, it will disable the system temporarily to prevent damage to the clutches.

Schematic Reference

All-Wheel Drive Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information.

1. Monitor the wheel speed sensors using the transfer case scan tool data list. If the wheel speeds are erratic or there is a large difference between front and rear then diagnose and repair as necessary. Check for EBCM DTCs as they have likely set for wheel speed performance.
2. While in a parking lot with a scan tool using transfer case special functions go to clutch coupling request and request 100%. Drive the vehicle while making sharp turns, if the vehicle binds on turns this indicates the system is working properly. If it does not bind on turns go to the next step.

Important: This test is intended for short duration use for testing purposes, long term use of this function at 100% request may result in extensive damage to the front axle or other driveline components.

3. If nothing is found with wheel speed performance then the clutches may be excessively worn. Refer to Transfer Case Disassemble.
4. Repair as necessary.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Transfer Case Disassemble