Four-Wheel Drive Does Not Engage

Four-Wheel Drive Does Not Engage





Test 1-8





Test 9-13

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 to it, an ignition 3 voltage circuit, ground circuit, axle actuator control circuit and an axle switch signal circuit.
Whenever a shift to 4WD is selected, the transfer case switch engages the front axle by grounding the axle actuator control circuit.

Test Description
The numbers below refer to the step numbers on the diagnostic table.
2. Tests for proper ignition 3 voltage to the front axle actuator.
3. Tests for proper ground at the front axle actuator.
4. Tests for proper ground at the axle actuator control circuit through the transfer case switch.
5. Tests the transfer case switch ground circuit for an open.
6. Tests the transfer case switch for proper operation.