Diagnostic System Check - Transfer Case

Diagnostic System Check - Transfer Case
These diagnostic procedures help you find and repair automatic transfer case (ATC) system malfunctions. This service category also contains information for repairing ATC system malfunctions. For best results, use the diagnostic tables and follow the sequence listed below:
1. Perform the Transfer Case Diagnostic System Check. All ATC diagnostics must begin with the Transfer Case Diagnostic System Check. The Transfer Case Diagnostic System Check determines the following:
^ Proper SERVICE 4WD indicator operation.
^ Ability of the transfer case shift control module to communicate through the Data Link Connector (DLC)
^ Existence of ATC DTCs

2. Refer to the diagnostic table as directed by the Transfer Case Diagnostic System Check. The diagnostic tables help enable you to diagnose any ATC system malfunction. Bypassing these procedures may result in the following:
^ Extended diagnostic time
^ Incorrect diagnosis
^ Incorrect parts replacement

3. Repeat the Transfer Case Diagnostic System Check after you perform any repair or diagnostic procedure. This verifies that you correctly performed the repair. This also ensures that other malfunctions do not exist.

Test Description

Steps 1-6:

The numbers below refer to the step numbers on the diagnostic table.
2. This step inspects for lack of communication that may be due to a partial malfunction of the Class 2 serial data circuit or due to a total malfunction of the Class 2 serial data circuit. The specified procedure determines the particular condition.
3. The presence of DTCs indicates that the transfer case shift control module has detected a fault. Go to symptoms for other concerns.
4. The presence of DTCs which begin with "U" indicate some other module is not communicating. The specified procedure compiles all the available information before tests are performed.
5. Vehicle speed is provided to the transfer case shift control module via Class 2 and can effect the setting of DTC C0300. Perform the diagnostics for powertrain DTC P0502 and DTC P0503 first.
6. Perform diagnostics for DTC C0300 and DTC C0305 first before addressing other DTCs. DTC C0300 and DTC C0305 can be responsible for setting other DTCs.