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.
Diagnostic Aids
A mechanical condition inside the front axle could prevent the shift fork from moving causing the motor to be stuck in one position. Refer to Symptoms - Front Drive Axle .
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 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 |
|---|---|---|---|---|
Schematic Reference: Transfer Case Control Schematics Connector End View Reference: Transfer Case Control Connector End Views | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |
Does the scan tool display Unlocked and Locked 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 open fuse in the front axle feed 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 front axle feed 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 switch/actuator. Refer to Electric Motor Actuator Replacement . Did you complete the repair? | -- | Go to Step 15 | -- |
14 | 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 |
