GM Service Manual Online
For 1990-2009 cars only

Step

Action

Yes

No

DEFINITION: 4WD indicator illuminated when ignition is ON. Transfer case and axle pump operate normally.

1

Did you review the transfer case operation and perform the necessary inspections?

Go to Step 2

Go to Transfer Case Diagnostic System Check

2

  1. Turn ON the ignition, with the engine OFF.
  2. Place the transfer case in 2WD.

Does the 4WD indicator turn off?

Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 3

3

Test the 4WD indicator circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 6

Go to Step 4

4

Is the transfer case stuck in 4WD?

Go to Transfer Case Diagnosis

Go to Step 5

5

Replace the PCM. Refer to PCM Replacement in Engine Controls.

Did you complete the repair?

Go to Step 6

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6

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3