Envoy 2WD V8-5.3L VIN P (2004)
Actuators and Solenoids - Differential: Customer Interest
4X4 System - Service 4WD Lamp ON/4WD Inoperative
Bulletin No.: 04-04-19-001
Date: February 23, 2004
TECHNICAL
Subject:
Diagnostic Trouble Code (DTC) C0379 Set, Service 4WD Light On, 4WD Inoperative (Replace Front Axle Actuator)
Models:
2004 Chevrolet TrailBlazer, TrailBlazer EXT
2004 GMC Envoy, Envoy XL, Envoy XUV
with Autotrac Active Transfer Case (RPO NP8)
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).
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
Important:
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 12471631.
Follow the service procedure below to replace the front axle actuator.
1.
Raise the vehicle.
2.
Remove the engine shield mounting bolts.
3.
Remove the engine shield.
4.
Disconnect the electrical connector from the actuator assembly.
