Front Axle Will Not Disengage

Front Axle Will Not Disengage

Circuit Description
The front axle control circuit consists of a front drive axle clutch solenoid, which is electronically controlled by the transfer case shift control module. The front drive axle clutch solenoid opens and closes a vacuum control valve, allowing vacuum to apply and release a clutch pack inside the front axle housing. The transfer case shift control module determines whether or not the clutch pack has been applied or released, based on a signal from the front axle switch mounted on the front axle housing assembly. The front axle is normally locked, or engaged, during AUTO 4WD, 4WD HI, and 4WD LO modes. The front axle is unlocked, or disengaged, only during 2HI or Neutral modes.

Steps 1-13:

Steps 14-18:

Test Description
These numbers correspond to the step numbers on the diagnostic table.
2. This step helps determine whether the transfer case shift control module has electronic control of the front axle actuator.
3. This step does a visual inspection of the front axle to determine if the front axle is mechanically engaged.
4. This step helps determine if the front axle control circuit is shorted to ground.
5. This step tests the front axle control circuit for a short to ground.
6. This step helps determine whether the short to ground is due to faulty wiring or a module.
7. This step helps determine a faulty front axle switch.
8. This step tests the front axle switch signal circuit for a short to voltage.
9. This step helps determine whether the short to voltage is due to faulty wiring or a module.
10. This step helps determine a faulty front axle actuator.