GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

Did you perform the transfer case Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check

2

Verify the fault is present.

Does the system operate normally?

--

Go to Testing for Electrical Intermittents

Go to Step 3

3

  1. Turn OFF the ignition.
  2. Disconnect the front axle actuator/switch.
  3. Ensure the four wheel drive (4WD) control lever is in the two wheel drive (2WD) position.
  4. Turn ON the ignition, with the engine OFF.
  5. Probe the ignition positive voltage circuit of the front axle actuator/switch with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

--

Go to Step 4

Go to Step 7

4

  1. Turn OFF the ignition.
  2. Probe the ground circuit of the front axle actuator/switch with a test lamp that is connected to a battery positive voltage circuit.

Does the test lamp illuminate?

--

Go to Step 5

Go to Step 8

5

Probe the front axle actuator/switch control circuit with a test lamp that is connected to a battery positive voltage circuit.

Does the test lamp illuminate?

--

Go to Step 6

Go to Step 10

6

  1. Disconnect the transfer case switch.
  2. Probe the front axle actuator/switch control circuit at the transfer case switch with a test lamp that is connected to a battery positive voltage circuit.

Does the test lamp illuminate?

--

Go to Step 9

Go to Step 11

7

Repair the open in ignition positive voltage circuit between the fuse and the front axle actuator/switch. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 12

--

8

Repair the open in the ground circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 12

--

9

Repair the short to ground in the front axle actuator/switch control circuit . Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 12

--

10

Replace the front axle actuator/switch. Refer to Electric Motor Actuator Replacement in Front Drive Axle.

Did you complete the replacement?

--

Go to Step 12

--

11

Replace the transfer case switch. Refer to Four-Wheel Drive Indicator Switch Replacement in Front Drive Axle.

Did you complete the replacement?

--

Go to Step 12

--

12

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 3