Circuit Description
The front axle control circuit consists of an electric motor actuator, which engages and disengages the front axle. The front axle actuator motor consists of a permanent magnetic motor, a worm gear controlled plunger, a front axle switch and an electronic control circuit, all within the actuator assembly.
The front axle actuator consists of the following circuits:
| • | The front axle control circuit, which is also connected to the transfer case shift control module |
| • | The front axle switch circuit, which is also connected to the transfer case shift control module |
| • | A battery feed circuit |
| • | A ground circuit |
When a shift to AUTO 4WD, 4HI, or 4LO is requested, the transfer case shift control module engages the front axle by grounding the front axle control circuit through a current limiting driver.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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This step tests the electrical function of the front axle actuator and helps determine between mechanical and electrical malfunctions.
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This step tests for proper power and ground at the front axle actuator.
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This step tests the operation of the front axle control circuit.
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This step helps determine if the transfer case shift control module is able to monitor the front axle switch.
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This step tests the front axle switch circuit for an open or high resistance.
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This step measures the voltage between the front axle feed circuit and ground.
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This step tests the front axle control circuit for an open or high resistance.
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This step inspects the front axle for a mechanical malfunction.
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This step tests for open fuse in the front axle feed circuit.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |
Does the front axle turn ON and OFF with each command? | -- | Go to Step 9 | Go to Step 3 | |
Is the voltage reading within the specified value? | 11-13 V | Go to Step 4 | Go to Step 7 | |
Does the test lamp illuminate? | -- | Go to Step 5 | Go to Step 8 | |
Does the scan tool display the Front Axle Switch status Locked? | -- | Go to Step 13 | Go to Step 6 | |
Test the front axle actuator signal circuit for an open or high resistance. Refer to Testing for Continuity and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 14 | |
Measure the voltage between the ignition 3 voltage circuit and ground. Is the voltage reading within the specified range? | 9-14 V | Go to Step 12 | Go to Step 10 | |
Test the front axle control circuit for an open or high resistance. Refer to Testing for Continuity and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 14 | |
Inspect the front axle for a mechanical malfunction. Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 13 | |
Test for an open fuse in the Ignition 3 voltage circuit. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 11 | |
11 | Repair an open in the Ignition 3 voltage circuit. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Step 15 | -- |
12 | Repair an open in the front axle ground circuit. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Step 15 | -- |
13 | Replace the front axle actuator. Refer to Front Drive Axle Actuator Replacement . Did you complete the repair? | -- | Go to Step 15 | -- |
14 |
Important: After transfer case shift control module replacement and reprogramming, ensure all doors are closed and the key is out of the ignition, then open and close the doors again and wait 2 minutes to avoid incomplete programming or false communication DTCs. Replace the transfer case shift control module. Refer to Control Module References for replacement, setup, and programming. Did you complete the repair? | -- | Go to Step 15 | -- |
15 |
Is the symptom still present? | -- | Go to Step 2 | System OK |
