Circuit Description
The front axle control circuit consists of an electric motor actuator which engages and disengages the front axle. The front axle actuator's motor consists of the following components within the actuator assembly:
| • | A permanent magnetic (PM) motor |
| • | A worm gear controlled plunger |
| • | A front axle switch |
| • | An electronic control circuit |
The front axle actuator has 4 circuits connected to the actuator:
| • | The ignition 3 voltage circuit |
| • | The ground circuit |
| • | The axle actuator control circuit |
| • | The 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.
This DTC detects a shorted actuator, or a short to 12 volt on the axle actuator control circuit.
Conditions for Setting the DTC
| • | The system will try to engage the front axle. If the system cannot engage the front axle, the system will not attempt the procedure again during that ignition cycle. |
| • | The transfer case shift control module reads back the front axle output as a high voltage when a low voltage is expected. |
Action Taken When the DTC Sets
| • | All shifting for 4WD mode will be disabled. |
| • | The SERVICE 4WD indicator lamp will be commanded ON for the remainder of the current ignition cycle. |
Conditions for Clearing the DTC
| • | The transfer case shift control module will clear the DTC if the Condition For Setting The DTC does not exist. |
| • | A history DTC will clear after 100 consecutive ignition cycle without a fault present. |
| • | History DTCs can be cleared using a scan tool. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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This step tests the operation of the front axle switch.
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This step tests the electrical control of the front axle switch.
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This step tests the axle actuator control circuit for a short to voltage.
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This step inspects for poor connections at the front axle actuator.
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This step inspects for poor connections at the harness connector, of the transfer case shift control module.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Transfer Case Control Schematics | |||
1 | Was the Transfer Case Diagnostic System Check performed? | Go to Step 2 | |
Does the front axle turn ON and OFF with each command? | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 3 | |
Does the test lamp turn ON and OFF with each command? | Go to Step 5 | Go to Step 4 | |
Test the axle actuator control circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 9 | Go to Step 6 | |
Inspect for poor connections at the front axle actuator. Refer to Circuit Testing , and to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 9 | Go to Step 7 | |
Inspect for poor connections at the harness connector. Refer to Testing for Intermittent Conditions and Poor Connections , and to Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 9 | Go to Step 8 | |
7 | Replace the front axle actuator. Refer to Electric Motor Actuator Replacement in Front Drive Axle. Did you complete the replacement? | Go to Step 9 | -- |
8 | Replace the transfer case shift control module. Refer to Transfer Case Shift Control Module Replacement . Did you complete the replacement? | Go to Step 9 | -- |
9 |
Does the DTC reset? | Go to Step 2 | System OK |
