GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2002 🢒 Envoy - 4WD 🢒 Driveline/Axle 🢒 Transfer Case - NVG 126-NP4 🢒 Service Indicator Always On

Circuit Description

The SERVICE AWD indicator is located in the instrument cluster and shares the instrument cluster common power and ground. The transfer case shift control module controls the SERVICE AWD indicator by sending the instrument cluster a Class 2 message. This lamp may be controlled with the scan tool using the instrument cluster device controls.

Test Description

The number below refers to the step number on the diagnostic table.

  1. This step determines whether the failure is the result of a malfunctioning transfer case shift control module or the instrument cluster.

Step

Action

Value(s)

Yes

No

1

Did you perform the Diagnostic System Check - Transfer Case?

--

Go to Step 2

Go to Diagnostic System Check - Transfer Case

2

  1. Turn the ignition ON, with the engine OFF.
  2. Install a scan tool.
  3. Using the scan tool, command the SERVICE AWD lamp OFF.

Does the SERVICE AWD lamp turn OFF?

--

Go to Step 3

Go to Diagnostic System Check - Instrument Cluster

3

Important: After transfer case shift control module replacement and reprogramming, ensure all doors are closed and the key is out of the ignition, then open and close the doors again and wait 2 minutes to avoid incomplete programming or false communication DTCs.

Replace the transfer case shift control module. Refer to Transfer Case Shift Control Module Replacement and Transfer Case Shift Control Module Reprogramming .

Did you complete the repair?

--

Go to Step 4

--

4
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the conditions for the symptom to occur.

Does the symptom occur?

--

Go to Step 2

System OK