GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2004 🢒 Safari - 4WD 🢒 Driveline/Axle 🢒 Transfer Case - NVG 136-NP4 🢒 Service All-Wheel Drive Indicator Always On

Circuit Description

The SERVICE AWD indicator is located in the instrument cluster. It receives ignition voltage through the instrument cluster 10 amp gage fuse through the ignition 1 voltage circuit. This circuit also supplies all of the gages with ignition voltage. The transfer case shift control module controls the SERVICE AWD indicator by sending the instrument cluster a Class 2 message. This indicator may be controlled with the scan tool using the instrument cluster output controls.

Test Description

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

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

Step

Action

Yes

No

Schematic Reference: Transfer Case Control Schematics

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 go to insturment panel cluster output controls.
  4. Use the scan tool in order to command the SERVICE 4WD Message OFF.

Does the SERVICE 4WD Message turn OFF?

Go to Step 3

Go to Instrument Panel Assembly Replacement in Instrument Panel, Gages and Console

3

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

Did you complete the repair?

Go to Step 4

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4
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle in order to determine if the symptom has been corrected.

Is the symptom still present?

Go to Step 2

System OK