GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2000 🢒 Jimmy - 4WD 🢒 Body and Accessories 🢒 Wiring Systems 🢒 Service Indicator Always On

Circuit Description

The SERVICE indicator (AWD/4WD) lamp 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 indicator (AWD/4WD) lamp 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

Value(s)

Yes

No

1

Was the Transfer Case Diagnostic System Check performed?

--

Go to Step 2

Go to Diagnostic System Check

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

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 symtom to re-occur.

Does the symtom to re-occur?

--

Go to Step 2

System OK