Were you sent here from a symptom table?

Go to Step 2

Go to Diagnostic Starting Point - Front Drive Axle

1. Start the engine.
2. Inspect the instrument panel to see if the Service 4WD light is illuminated.

Does the Service 4WD light stay illuminated with the engine running?

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

Go to Step 3

Inspect the vacuum hoses for the following:

Are the vacuum hoses kinked, plugged, damaged, or disconnected?

Go to Step 4

Go to Step 5

Repair or replace the vacuum hoses as necessary.

Does the front drive axle engage?

System OK

Go to Step 5

1. Press the 4HI button to attempt to engage the front drive axle.
2. Disconnect the vacuum hose from the vacuum actuator.
3. Inspect for vacuum at the vacuum actuator.

Is there vacuum at the vacuum actuator connection?

Go to Step 6

Go to Step 7

Replace the vacuum actuator. Refer to Front Drive Axle Actuator Replacement .

Does the front drive axle engage?

System OK

Go to Step 8

Replace the vacuum actuator solenoid valve. Refer to Vacuum Actuator Solenoid Valve Replacement .

Does the front drive axle engage?

System OK

Go to Step 8

Inspect the clutch cable for the following:

Is the clutch cable damaged, binding or disconnected?

Go to Step 9

Go to Step 10

Replace the clutch cable. Refer to Clutch Cable Replacement - Front Drive Axle .

Does the front drive axle engage?

System OK

Go to Step 10

1. Disconnect the clutch cable from the clutch fork. Refer to Clutch Cable Replacement - Front Drive Axle .
2. Inspect the operation of the clutch fork using the J 33798 .

Does the front drive axle engage?

System OK

Go to Step 11

Replace the clutch fork. Refer to Front Drive Axle Clutch Fork Replacement .

Does the front drive axle engage?

System OK

Go to Step 12

The cause of concern may be in the front drive axle. Disassemble the front drive axle. Inspect for damaged components and repair as necessary. Refer to Differential Carrier Assembly Disassemble .

Does the front drive axle engage?

System OK

Go to Step 1

Were you sent here from a symptom table?

Go to Step 2

Go to Diagnostic Starting Point - Front Drive Axle

Check the transfer case shift control module for DTC. Refer to Diagnostic Trouble Code (DTC) Displaying in Transfer Case - NVG 233-NP1.

Are any DTCs present?

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

Go to Step 3

Inspect the vacuum hoses for the following:

Are the vacuum hoses kinked, plugged, damaged, or disconnected?

Go to Step 4

Go to Step 5

Repair or replace the vacuum hoses as necessary.

Does the front drive axle engage?

System OK

Go to Step 5

1. Press the 4HI button to attempt to engage the front drive axle.
2. Disconnect the vacuum hose from the vacuum actuator.
3. Inspect for vacuum at the vacuum actuator.

Is there vacuum at the vacuum actuator connection?

Go to Step 6

Go to Step 7

Replace the vacuum actuator. Refer to Front Drive Axle Actuator Replacement .

Does the front drive axle engage?

System OK

Go to Step 8

Replace the vacuum actuator switch. Refer to Transfer Case Vacuum Switch Replacement in Transfer Case - NVG 233-NP1.

Does the front drive axle engage?

System OK

Go to Step 8

Inspect the clutch cable for the following:

Is the clutch cable damaged, binding, or disconnected?

Go to Step 9

Go to Step 10

Replace the clutch cable. Refer to Clutch Cable Replacement - Front Drive Axle .

Does the front drive axle engage?

System OK

Go to Step 10

1. Disconnect the clutch cable from the clutch fork. Refer to Clutch Cable Replacement - Front Drive Axle .
2. Inspect the operation of the clutch fork using the J 33798 Hub Engagement Tool.

Does the front drive axle engage?

System OK

Go to Step 11

Replace the clutch fork. Refer to Front Drive Axle Clutch Fork Replacement .

Does the front drive axle engage?

System OK

Go to Step 12

The cause of concern may be in the front drive axle. Disassemble the front drive axle. Inspect for damaged components and repair as necessary. Refer to Differential Carrier Assembly Disassemble .

Does the front drive axle engage?

System OK

Go to Step 1