GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2003 🢒 GMC Sierra Denali 🢒 Driveline/Axle 🢒 Transfer Case - NVG 263-NP1 🢒 Diagnostic System Check - Transfer Case

Important: Read the Transfer Case Description and Operation to familiarize yourself with basic system operation. Refer to Transfer Case Description and Operation .

Test Description

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

  1. This step checks that the scan tool is communicating with the transfer case shift control module (TCCM).

    2.

  2. This step checks the presence of DTCs which begin with "U" indicating some other module is not communicating.

    3.

  3. This step checks to see if other modules are interfering with the TCCM operation.

  4. This step checks for TCCM DTCs.

    5.

  5. This step verifies if the TCCM has power and ground. The TCCM will not communicate without the Battery Positive Voltage circuit functioning.

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: A new TCCM from the manufacturer comes with the latest calibrations for that vehicle. A Service/Replacement TCCM does not come with vehicle specific calibrations. If the scan tool does not communicate with the TCCM, it may be due to incomplete or missing files. Refer to Transfer Case Shift Control Module Reprogramming .

  1. Turn ON the ignition, with the engine OFF.
  2. Attempt to establish communication with the TCCM.

Does the scan tool communicate with the TCCM?

Go to Step 3

Go to Step 7

3

Does the scan tool display any current DTCs which begin with a "U"?

Go to Scan Tool Does Not Communicate with Class 2 Device in Data Link Communications

Go to Step 4

4

Does the scan tool display any VSS DTCs?

Go to Diagnostic System Check - Automatic Transmission in Automatic Transmission - 4L80-E/4L85-E or Diagnostic System Check - Automatic Transmission in Automatic Transmission - Allison

Go to Step 5

5

Does the scan tool display any Electronic Brake Control Module (EBCM) DTCs?

Go to Diagnostic System Check - ABS in Antilock Brake System

Go to Step 6

6

Does the scan tool display any TCCM DTCs?

Go to Diagnostic Trouble Code (DTC) List

Go to Symptoms - Transfer Case

7

Important: If there are multiple TCCM DTCs, diagnose the DTCs in the order listed in the DTC list.

Test the battery positive voltage, ATC Class 2 Serial Data and ground circuits of the TCCM for an open, high resistance, short to ground and short to voltage.

Did you find a condition with the circuits?

Go to Step 9

Go to Step 10

8
  1. Flash the TCCM with the most current calibrations.
  2. Test drive the vehicle.

Did the 4WD system operate normally without setting any DTCs?

System OK

Go to Step 3

9

Repair the open, high resistance or short in the affected circuits.

Did you complete the repair?

Go to Step 11

--

10

Replace the TCCM. Refer to Transfer Case Shift Control Module Replacement and Transfer Case Shift Control Module Reprogramming .

Did you complete the replacement?

Go to Step 11

--

11

Test drive the vehicle.

Does the vehicle 4WD system operate normally without setting any DTCs?

System OK

Go to Step 1