Front Axle Will Not Engage

Front Axle Will Not Engage

Diagnostic Instructions

* Perform theDiagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* ReviewStrategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.



Circuit/System 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 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
* An ignition 3 voltage 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.


Reference Information
Schematic Reference

Transfer Case Control Schematics (MP 3023/3024-NQH - Transfer Case)
Connector End View Reference

Component Connector End Views (Connector Views)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information.


Circuit/System Testing

1. If this is occurring without DTC C0379 setting it is likely related to a mechanical issue. Refer to Four-Wheel Drive Does Not Engage (Four-Wheel Drive Does Not Engage) .
2. If no mechanical issue is found replace the front axle actuator.



Repair Instructions

Perform theDiagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Control Module References (Programming and Relearning) for TCSCM replacement, setup, and programming
* Transfer Case High/Low Clutch Reset (Transfer Case High/Low Clutch Reset)
* Four-Wheel Drive Does Not Engage (Four-Wheel Drive Does Not Engage)
* Four-Wheel Drive Does Not Disengage (Four-Wheel Drive Does Not Disengage)
* Front Drive Axle Actuator Replacement (Service and Repair)