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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1254 (Transfer Case - NVG 246-NP8 (Two Speed Automatic)) >> Diagnostic Information and Procedures >> Front Axle Will Not Engage >> Test Description

Test Description

WARNING: This page is about a different car, the 2002 GMC Yukon XL, 2002 GMC Yukon, 2002 Chevrolet Tahoe, 2002 Chevrolet Suburban, and 2002 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.

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

  1. 2:  Tests the electrical function of the front axle actuator. Helps determine between mechanical and electrical malfunctions.
  2. 3:  Tests for proper power and ground at the front axle actuator.
  3. 4:  Tests the operation of the front axle control circuit.
  4. 5:  Helps determine if the transfer case shift control module is able to monitor the front axle switch.
  5. 6:  Tests the front axle switch circuit for an open or high resistance.
  6. 7:  Measures the voltage between the front axle feed circuit and ground.
  7. 8:  Tests the front axle control circuit for an open or high resistance.
  8. 9:  Inspects the front axle for a mechanical malfunction.
  9. 10:  Tests for open in the front axle feed circuit.
Front Axle Will Not Engage

Step Action Value(s) Yes No
Schematic Reference:  Transfer Case Control Schematics  
1 Was the Transfer Case Diagnostic System Check performed? - Go to Step 2  Go to Diagnostic System Check - Transfer Case 
2 
  1. Install a scan tool.
  2. Turn the ignition ON, with the engine OFF.
  3. With a scan tool, command the front axle Unlocked and Locked.
Does the front axle turn ON and OFF with each command?		 - Go to Step 9  Go to Step 3 
3 
  1. Turn the ignition OFF.
  2. Disconnect the front axle actuator.
  3. Turn the ignition ON, with the engine OFF.
  4. Measure the voltage between the front axle feed circuit and the front axle ground circuit at the front axle actuator.
Is the voltage reading within the specified values?		 9-14 V Go to Step 4  Go to Step 7 
4 
  1. Connect a test lamp between the front axle feed circuit and the front axle control circuit at the front axle actuator.
  2. Observe the test lamp, while using the scan tool in order to engage the front axle.
Does the test lamp light?		 - Go to Step 5  Go to Step 8 
5 
  1. Connect a fused jumper wire between the front axle feed circuit and the front axle switch circuit.
  2. Use the scan tool in order to read the Front Axle Switch status.
Does the scan tool display the Front Axle Switch status Locked?		 - Go to Step 12  Go to Step 6 
6  Test the front axle switch circuit for an open or high resistance. Refer to CIRCUIT TESTING and WIRING REPAIRS in Wiring Systems.
Was the condition found and corrected?		 - Go to Step 14  Go to Step 13 
7  Measure the voltage between the front axle feed circuit and ground.
Is the voltage reading within the specified values?		 9-14 V Go to Step 11  Go to Step 10 
8  Test the front axle control circuit for an open or high resistance. Refer to CIRCUIT TESTING and WIRING REPAIRS in Wiring Systems.
Was the condition found and corrected?		 - Go to Step 14  Go to Step 13 
9  Inspect the front axle for a mechanical malfunction.
Was the condition found and corrected?		 - Go to Step 14  Go to Step 12 
10  Repair an open in the front axle feed circuit. Refer to CIRCUIT TESTING and WIRING REPAIRS in Wiring Systems.
Is the repair complete?		 - Go to Step 14  -
11 Repair an open in the front axle ground circuit. Refer to CIRCUIT TESTING and WIRING REPAIRS in Wiring Systems.
Is the repair complete?		 - Go to Step 14  -
12 Replace the front axle switch/actuator. Refer to ELECTRIC MOTOR ACTUATOR REPLACEMENT .
Is the repair complete?		 - Go to Step 14  -
13 Replace the transfer case shift control module. Refer to Transfer Case Shift Control Module Replacement .
Is the repair complete?		 - Go to Step 14  -
14
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for allowing the symptom to re-occur.
Does the symptom re-occur?		 - Go to Step 2  System OK
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