1. Connect a scan tool.
2. Turn ignition the ON.
3. Turn the engine OFF.
4. Using a scan tool, test for any DTCs in the Instrument Cluster.

Does the scan tool show any DTCs?

--

Refer to Instrument Cluster System Check in instrument panel, gauges and console

Go to Step 2

Does the front axle disengage when the four wheel drive (4WD) control lever is in the two wheel drive (2WD) position?

--

Go to Step 3

Refer to Front Axle Will Not Disengage

Using the scan tool, under special test in instrument cluster, command the 4WD indicator lamp OFF.

Does the lamp go out?

--

Go to Step 4

Refer to Instrument Cluster System Check in instrument panel, gauges and console

1. Ensure the 4WD control lever is in the 2WD position.
2. Using the scan tool, under engine controls, PCM/VCM, read the front axle switch status.

Does the scan tool show switch status no?

--

Go to Step 8

Go to Step 5

1. Disconnect the front axle actuator/switch.
2. Using the scan tool, under engine controls, PCM/VCM,read the front axle switch status.

Does the scan tool show switch status nNo?

--

Go to Step 6

Go to Step 7

Replace the front axle actuator/switch. Refer to Electric Motor Actuator Replacement .

Is the repair complete?

--

System OK

--

1. Turn the ignition OFF.
2. Disconnect the VCM/PCM.
3. Turn the ignition ON.
4. Turn the engine OFF.
5. Using a DMM, measure the voltage from terminal A of the switch to ground.

Is the voltage within the specified value?

0-0.5 V

Go to Step 8

Go to Step 9

Replace the VCM/PCM. Refer to VCM Replacement/Programming for 4.3L or Powertrain Control Module Replacement/Programming for all other engines in Engine Controls.

Is the repair complete?

--

System OK

--

Locate and repair the CKT 1695 (BLK/WHT) for a short to voltage.

Is the repair complete?

--

System OK

--