GM Service Manual Online
For 1990-2009 cars only

Important: Perform the Diagnostic System Check - Vehicle in Vehicle DTC Information before using the symptom tables, in order to verify that the following conditions are true:

   • There are no diagnostic trouble codes (DTCs) set.
   • The control module or modules can communicate via the serial data link.

    • Review the system operation in order to familiarize yourself with the system functions. Refer to Transfer Case Description and Operation .
    • Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.
    •  Inspect the automatic transfer case for the proper fluid level.

Intermittent

Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. Some symptoms may be caused by loose wiring. Be sure to test the system after moving or connecting harnesses, but before replacing parts.

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom:

    •  Transfer Case Shift Control Switch Inoperative
    •  Transfer Case Shift Control Switch Indicator Always On - Two or More
    •  Transfer Case Shift Control Switch Indicator Flashes, then Returns to Previous Mode
    •  Transfer Case Shift Control Switch Indicator Inoperative - One or More
    •  Transfer Case Will Not Shift
    •  Transfer Case Popping Noise
    •  Transfer Case Whine or Rumble Noise
    •  Transfer Case Growl or Grinding Noise
    •  Transfer Case Clunk in 2HI Only
    •  Transfer Case Clunk in 4HI
    •  Transfer Case Clunk in 4LO
    •  Transfer Case Shudder or Binding
    •  Transfer Case Jumps Out of Gear