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 4WD position.
  4. Turn ON the ignition with the engine OFF.
  5. Probe the ignition positive voltage circuit with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

--

Go to Step 4

Go to Step 8

4

Probe the front axle acutator/switch ground circuit 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 9

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 12

Go to Step 6

6

  1. Disconnect the transfer case switch.
  2. Probe the transfer case switch ground circuit with a test lamp that is connected to a battery positive voltage circuit.

Does the test lamp illuminate?

--

Go to Step 7

Go to Step 10

7

  1. Connect a 3 amp fused jumper wire between the front axle actuator/switch control circuit to a good ground.
  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 13

Go to Step 11

8

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

Did you complete the repair?

--

Go to Step 14

--

9

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

Did you complete the repair?

--

Go to Step 14

--

10

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

Did you complete the repair?

--

Go to Step 14

--

11

Repair the open in front axle actuator/switch control circuit between the switch and the actuator. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 14

--

12

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

Did you complete the repair?

--

Go to Step 14

--

13

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

Did you complete the repair?

--

Go to Step 14

--

14

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 3