GM Service Manual Online
For 1990-2009 cars only

Four-Wheel Drive Does Not Disengage S4WD

Step

Action

Yes

No

1

Were you sent here from a symptom table?

Go to Step 2

Go to Diagnostic Starting Point - Front Drive Axle

2

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

Are any DTCs present?

Go to Diagnostic Trouble Code (DTC) List in Transfer Case - NVG 233-NP1

Go to Step 3

3

Inspect the vacuum hoses for the following:

    • Kinks
    • Plugged
    • Damage

Are the vacuum hoses kinked, plugged, or damaged?

Go to Step 4

Go to Step 5

4

Repair or replace the vacuum hoses as necessary.

Does the front drive axle disengage?

System OK

Go to Step 5

5

  1. Disconnect the vacuum hose at the vacuum actuator.
  2. Inspect the vacuum actuator for movement.

Does the vacuum actuator move to disengage the front drive axle?

Go to Step 6

Go to Step 7

6

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

Does the front drive axle disengage?

System OK

Go to Step 8

7

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

Does the front drive axle disengage?

System OK

Go to Step 8

8

Inspect the clutch cable for the following:

    • Damage
    • Binding

Is the clutch cable damaged or binding?

Go to Step 9

Go to Step 10

9

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

Does the front drive axle disengage?

System OK

Go to Step 10

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 disengage?

System OK

Go to Step 11

11

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

Does the front drive axle disengage?

System OK

Go to Step 12

12

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

Does the front drive axle disengage?

System OK

Go to Step 1