Front Axle Will Not Engage

Front Axle Will Not Engage





Test 1-2





Test 3-15

Circuit Description
The front axle control circuit consists of an electric motor actuator which engages and disengages the front axle. The front axle actuator consists of a Permanent Magnetic (PM) motor, a worm gear controlled plunger, a front axle switch and an electronic control circuit all within the actuator assembly.
The front axle actuator has four circuits connected:
^ Ignition 3 voltage circuit
^ Ground circuit
^ Axle actuator control circuit
^ Axle switch signal circuit
Whenever a shift to 4HI, or 41-0 is requested, the transfer case shift control module engages the front axle by grounding the axle actuator control circuit through a current limiting driver.

Test Description
The numbers below refer to the step numbers on the diagnostic table.
2. This step tests the electrical function of the front axle actuator. This step helps determine between mechanical and electrical malfunctions.
3. This step tests for proper power and ground at the front axle actuator.
4. This step tests the operation of the axle actuator control circuit.
5. This step helps determine if the transfer case shift control module is able to monitor the front axle switch.
6. This step tests the axle switch signal circuit for an open or high resistance.
7. This step measures the voltage between the ignition 3 voltage circuit and ground.
8. This step tests the axle actuator control circuit for an open or high resistance.
9. This step inspects the front axle for a mechanical malfunction.
10. This step tests for open fuse in the ignition 3 voltage circuit.