Front Axle Will Not Disengage

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 4LO 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. 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 tests the electrical function of the axle actuator control circuit.

6. This step tests for proper ignition 3 voltage to the front axle actuator.

7. This step tests for open fuse in the ignition 3 voltage circuit.

8. This step tests the axle actuator control circuit for an open or high resistance.

9. This step tests the axle switch signal circuit for an open or high resistance.

10.This step helps determine if the front axle actuator has a mechanical malfunction.

11.This step tests the axle switch signal circuit for a short to voltage.

12.Inspect the front axle for a mechanical malfunction.

Step Action Value(s) Yes No Schematic Reference: 1 Was the Transfer Case Diagnostic System -- Go to Go to Diagnostic Check performed? Step 2 System Check - Transfer Case 1. Turn ON the ignition, with the engine OFF. 2. Ensure that the vehicle is in 2WD mode. 3. Install a scan tool. 4. Use the scan tool in order to read the Front 2 -- Axle Switch Status.

Does the scan tool display the Front Axle Switch Go to status as Locked? Step 10 Go to Step 3 1. Turn OFF the ignition. 2. Disconnect the front axle actuator. 3. Turn ON the ignition, with the engine OFF. 4. Measure the voltage between the ignition 3 3 voltage circuit and the ground circuit at the 9-14 V front axle actuator.

Does the voltage measure within the specified Go to values? Step 4 Go to Step 6 1. Connect a test lamp between the ignition 3 voltage circuit and the axle actuator control circuit at the front axle actuator. 4 2. Observe the test lamp, while using the scan -- tool in order to engage the front axle. Go to Does the test lamp illuminate? Step 5 Go to Step 8 1. Connect a fused jumper wire between the ignition 3 voltage circuit and the axle switch signal circuit. 2. Use the scan tool in order to read the Front 5 -- Axle Switch status.

Does the scan tool display the Front Axle Switch Go to status Locked? Step 15 Go to Step 9 Measure the voltage between the ignition 3 voltage circuit and ground. 6 9-14 V Does the voltage measure within the specified Go to values? Step 13 Go to Step 7 Test for open fuse in the ignition 3 voltage 7 circuit. -- Go to Did you find and correct the condition? Step 17 Go to Step 14 Test the axle actuator control circuit for an open 8 or high resistance. -- Go to Did you find and correct the condition? Step 17 Go to Step 16 Test the axle switch signal circuit for an open or 9 high resistance. -- Go to Did you find and correct the condition? Step 17 Go to Step 16 10 1. Disconnect the front axle actuator. -- Go to Go to Step 12 2. Use the scan tool in order to read the Front Step 11 Axle Switch status.

Does the scan tool display the Front Axle Switch status Locked? Test the axle switch signal circuit for a short to 11 voltage -- Go to Did you find and correct the condition? Step 17 Go to Step 16 Inspect the front axle for a mechanical 12 malfunction. -- Go to Did you find and correct the condition? Step 17 Go to Step 16 Repair an open in the ground circuit. Go to 13 -- Did you complete the repair? Step 17 -- Repair an open in the ignition 3 voltage circuit. Go to 14 -- Did you complete the repair? Step 17 -- Replace the front axle actuator. Refer to the 15 Electric Motor Actuator Replacement . -- Go to Did you complete the replacement? Step 17 -- Replace the transfer case shift control module. Go to 16 Did you complete the replacement? -- Step 17 -- 1. Use the scan tool in order to clear the DTCs . 2. Operate the vehicle within the conditions for 17 allowing the symptom to re-occur. Go to Does the symptom re-occur? -- Step 2 System OK