Front Axle Will Not Engage

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. This 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 2 Hi or neutral modes.









Test Description
The number(s) below refer to the step number(s) on the diagnostic table.
2. Helps determine whether the transfer case shift control module has electronic control of the front axle actuator.
3. Tests the operation of the front axle switch by determining whether the state of the front axle switch is correct.
4. Determines whether correct vacuum is supplied to the front axle actuator.
5. Tests for proper voltage supplied to the front axle solenoid.
6. Helps determine continuity through the front axle control circuit (testing the wiring and module driver).
7. Tests the front axle circuit for an open.
8. Tests the front axle switch for an internal open.
9. Tests the front axle switch feed circuit for proper voltage.
10. Tests the front axle switch circuit for an open.