Test Description

WARNING: This page is about a different car, the 2003 GMC Sierra, 2003 GMC Cab & Chassis Sierra, 2003 Chevrolet Silverado, and 2003 Chevrolet Cab & Chassis 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.

2. This step checks that the scan tool is communicating with the transfer case shift control module (TCCM).
3. This step checks the presence of DTCs which begin with"U" indicating some other module is not communicating.
4. This step checks to see if other modules are interfering with the TCCM operation.
6. This step checks for TCCM DTCs.
7. This step verifies if the TCCM has power and ground. The TCCM will not communicate without the Battery Positive Voltage circuit functioning.

Fig 1: Diagnostic System Check - Transfer Case (Steps 1-7)

Courtesy of GENERAL MOTORS CORP.

Fig 2: Diagnostic System Check - Transfer Case (Steps 8-11)

Courtesy of GENERAL MOTORS CORP.