GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The Service indicator (AWD/4WD) lampis located in the instrument cluster. It receives ignition voltage from a 10 amp. gauge fuse through circuit 39. This circuit also supplies all of the gauges with ignition voltage. The automatic transfer case control module controls the Service indicator (AWD/4WD) lamp by sending the instrument cluster a Class 2 message. This lamp maybe control with the scan tool using the instrument cluster device controls.

Service Indicator Does Not Light

Step

Action

Value(s)

Yes

No

1

Was the Transfer Case Diagnostic System Check performed?

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Go to Step 2

Go to Transfer Case Diagnostic System Check

2

  1. Place the transmission in Park.
  2. Turn the ignition ON, engine OFF.
  3. Use the Scan Tool in order to command the Service 4WD Lamp On.

Does the Service 4WD Lamp light?

--

Go to Step 3

Go to Diagnostic System Check - Instrument Cluster

3

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

Is the repair complete?

--

Go to Step 4

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4

Reconnect all ATC system components, make sure all the components are properly mounted.

Have all the ATC components been reconnected and properly mounted?

--

Go to Step 5

--

5

Clear all ATC DTCs.

Have all the ATC DTCs been cleared?

--

Go to Transfer Case Diagnostic System Check

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