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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 971 (Transfer Case - NVG 246-NP8) >> Diagnostic Information and Procedures >> Diagnostic System Check - Transfer Case >> Test Description

Test Description

WARNING: This page is about a different car, the 2004 GMC Sierra and 2004 Chevrolet Silverado. 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:  This step inspects for lack of communication that may be due to a partial malfunction of the Class 2 serial data circuit or due to a total malfunction of the Class 2 serial data circuit. The specified procedure determines the particular condition.
  2. 3:  The presence of DTCs indicates that the transfer case shift control module has detected a fault. Go to symptoms for other concerns.
  3. 4:  The presence of DTCs which begin with "U" indicate some other module is not communicating. The specified procedure compiles all the available information before tests are performed.
  4. 5:  Vehicle speed is provided to the transfer case shift control module via Class 2 and can effect the setting of DTC C0300. Perform the diagnostics for powertrain DTC P0502 and DTC P0503 first.
  5. 6:  Perform diagnostics for DTC C0300 and DTC C0305 first before addressing other DTCs. DTC C0300 and DTC C0305 can be responsible for setting other DTCs.
Diagnostic System Check - Transfer Case

Step Action Yes No
1 Install a scan tool.
Does the scan tool power up?		 Go to Step 2  Go to Scan Tool Does Not Power Up in Data Link Communications
2 
    IMPORTANT: The ATC module does not come from the manufacturer already programmed. Use the scan tool to program the module with the latest calibrations, failure to do so causes no communications with the ATC module.
  1. Turn ON the ignition, with the engine OFF.
  2. Attempt to establish communication with the transfer case shift control module.
Does the scan tool communicate with the transfer case shift control module?		 Go to Step 3  Go to Scan Tool Does Not Communicate with Class 2 Device in Data Link Communications
3  Select the Transfer Case Shift Control Module display DTCs function on the scan tool.
Does the scan tool display any DTCs?		 Go to Step 4  Go to Symptoms - Transfer Case 
4  Does the scan tool display any DTCs which begin with a "U"? Go to Scan Tool Does Not Communicate with Class 2 Device in Data Link Communications Go to Step 5 
5  Does the scan tool display DTC P0502 or P0503? Go to Applicable Powertrain OBD Diagnostic System Check Go to Step 6 
6  Does the scan tool display DTC C0300 or C0305? Go to DTC C0300  or DTC C0305  Go to Diagnostic Trouble Code (DTC) List 
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