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Home >> GMC >> 2006 >> Sierra 1500 HD, RWD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 15 (Transfer Case - NVG 263-NP1 - Service & Diagnosis) >> Diagnostic Information and Procedures >> DTC C0379 >> Test Description

Test Description

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The numbers below refer to the step numbers on the diagnostic table.

  1. 2:  This step tests the front axle circuit for a current malfunction.
  2. 3:  This step helps determine if the failure is the result of a short to voltage or ground.
  3. 4:  This step helps determine if the front axle control circuit is shorted to ground.
  4. 5:  This step tests the integrity of the front axle switch and the ignition 3 voltage circuits.
  5. 6:  This step tests the front axle control circuit for short to ground.
  6. 7:  This step tests the front axle control circuit for short to voltage or ground.
  7. 8:  This step tests the front axle switch signal circuit for a short to voltage.
  8. 9:  This step tests the front axle ignition 3 voltage circuit and the front axle switch circuit for an open or short to ground.
  9. 10:  This step tests the front axle control circuit and the front axle ground circuit for an open or high resistance.
DTC C0379

Step Action 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  Go to Diagnostic System Check - Vehicle
2
  1. Install a scan tool.
  2. Turn the ignition ON, with the engine OFF.
  3. Place the transfer case into 2WD mode and change to 4WD.
  4. With a scan tool, observe the Front Axle Switch parameter.
Does the Front Axle Switch parameter change from Unlocked to Locked?		 Go to Testing for Intermittent Conditions and Poor Connections Go to Step 3 
3 Place the transfer case into 2WD mode.
Does the scan tool parameter continue to display Locked?		 Go to Step 4  Go to Step 5 
4 Disconnect the front axle switch/actuator.
Does the parameter display Unlocked?		 Go to Step 6  Go to Step 8 
5
  1. Turn the ignition OFF.
  2. Disconnect the front axle switch/actuator.
  3. Turn the ignition ON, with the engine OFF.
  4. Connect a fused jumper across the ignition 3 voltage and the axle switch signal circuits.
  5. With a scan tool, observe the Front Axle Switch parameter.
Does the Front Axle Switch parameter change from Unlocked to Locked?		 Go to Step 11  Go to Step 10 
6
  1. Turn the ignition OFF and disconnect the TCCM connectors C1 and C2.
  2. Test the front axle actuator control circuit for short to ground. Refer to Testing for Short to Ground and Wiring Repairs .
Did you find and correct the condition?		 Go to Step 13  Go to Step 7 
7 
  1. With the transfer case shift control module connected, turn the ignition ON, with the engine OFF.
  2. Place the transfer case into 2WD.
  3. Use a DMM to probe the front axle control circuit and check the module for an internal short to ground or voltage. Refer to Circuit Testing and Wiring Repairs .
Did the DMM indicate continuity to ground?		 Go to Step 12  Go to Step 9 
8
  1. Turn the ignition OFF.
  2. Disconnect the transfer case shift control module.
  3. Test the front axle switch signal circuit at the front axle actuator connector for a short to voltage.

    refer to Testing for a Short to Voltage .

Did you find and correct the condition?		 Go to Step 13  Go to Step 12 
9
  1. Connect the transfer case control module connectors C1 and C2.
  2. Test the front axle switch signal circuit for short to voltage. Refer to Testing for a Short to Voltage and Wiring Repairs .
Did you find and correct the condition?		 Go to Step 12  Go to Step 10 
10 Test the front axle ignition 3 circuit, the front axle switch circuit, and the front axle control actuator ground 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 13  Go to Step 12 
11 Replace the front axle switch/actuator. Refer to Electric Motor Actuator Replacement .
Did you complete the repair?		 Go to Step 13  -
12 Replace the transfer case shift control module. Refer to Control Module References for replacement, set-up, and programming.
Did you complete the repair?		 Go to Step 13  -
13
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.
Does the DTC set?		 Go to Step 2  System OK
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