GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2001 🢒 Sonoma Pickup - 4WD 🢒 Driveline/Axle 🢒 Transfer Case - NVG 136-NP4 (One Speed Automatic) 🢒 Service Indicator Always On

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.

Service Indicator Stays On When Key is On

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 Lamp OFF.

Does the Service 4WD Lamp turn OFF?

Go to Step 3

Go to Diagnostic System Check - Instrument Cluster

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