GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2001 🢒 Sonoma Pickup - 2WD 🢒 Driveline/Axle 🢒 Transfer Case - NVG 236/246-NP8 (Two Speed Automatic) 🢒 Service Indicator Always On

Circuit Description

The SERVICE 4WD indicator is located in the instrument cluster. It receives ignition voltage from a 10 amp gauge fuse through the instrument cluster feed circuit. This circuit also supplies all of the gauges with ignition voltage. The transfer case shift control module controls the SERVICE 4WD 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 numbers below refer to the step numbers on the diagnostic table.

  1. 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 Transfer Case Diagnostic System Check?

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. 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 Cluster Replacement in Instrument Panel, Gages and Console

3

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

Is the repair complete?

Go to Step 4

--

4
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for allowing the symptom to re-occur.

Does the symptom to re-occur?

Go to Step 2

System OK