4X4 System - Inoperative/DTC C0379/Svc. 4WD Lamp ON
TSB SB04-05-S007Diagnostic Trouble Code (DTC) C0379 Set, Service 4WD
Light ON, 4WD Inoperative
ISSUE DATE: JULY 2004
Affected Vehicles
2004 Isuzu Ascender (US/UT) models with Autotrac Active Transfer Case (RPO NP8).
Service Information
Condition:
Some customers may comment that the Service 4WD light is on and/or the 4WD system will not engage. This condition may only occur after a cold temperature start-up (typically below -6°C to -1°C (20°F to 30°F).
Possible Cause:
If this concern is accompanied by an illuminated "Service 4WD" light, and a DTC C0379, during a cold weather start up, the following information may apply.
The front drive axle actuator assembly engages the front axle in response to commands from the Transfer Case Control Module (TCCM). Normally, the cycle time for engagement is under 3 seconds, regardless of temperature. If the actuator does not engage the front axle assembly within 10 seconds, the TCCM sets DTC C0379, illuminates the "Service 4WD" light and disables the 4WD system. There have been reports of vehicles with front drive axle actuator assemblies that take longer than 10 seconds to engage, setting this code.
Correction:
Replace the front axle actuator.
Service Procedure
NOTE:
^ When a vehicle with this concern is diagnosed in the repair facility, usually the inside temperature is warm enough that the system operates normally, and the C0379 will be set as a history code, making the concern intermittent and difficult to diagnose.
^ If following the diagnostic chart for C0379 does not reveal another cause for the code, and the temperature was below approximately -1°C (30°F) when the customer noticed the condition, replace the front drive axle actuator assembly with P/N 8-12471-631-0.
1. Raise the vehicle, refer to Lifting and Jacking the Vehicle in the General Information section of the Service Manual.
2. Remove the engine shield mounting bolts.
3. Remove the engine shield.
4. Disconnect the electrical connector from the actuator assembly.
5. Remove the actuator assembly bolts (see figure 1).
6. Remove the actuator assembly.
7. Install the new actuator assembly.
8. Install the actuator assembly bolts and tighten to 6 N.m (53 lb in).
NOTE:
^ Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.
9. Connect the electrical connector to the actuator assembly.
10. Install the engine shield.
11. Install the engine shield mounting bolts and tighten to 25 N.m (18 lb ft).
12. Lower the vehicle and test.
Parts Information
Warranty Claim Information
Use the labor operation shown.
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