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:
• | Proper SERVICE 4WD indicator operation. |
• | The ability of the transfer case shift control module to communicate through the Data Link Connector (DLC). |
• | The existence of transfer case DTCs. |
• | Extended diagnostic time |
• | Incorrect diagnosis |
• | Incorrect parts replacement |
The numbers below refer to the step numbers on the diagnostic table.
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.
The presence of DTCs indicates that the transfer case shift control module has detected a fault. Go to symptoms for other concerns.
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.
Vehicle speed is provided to the transfer case shift control module via Class 2 and can effect transfer case shifting. Perform the diagnostics for powertrain DTC P0502 and DTC P0503 first.
Step | Action | Yes | No |
---|---|---|---|
1 | Install a scan tool. Does the scan tool power up? | Go to Step 2 | Go to Scan Tool Does Not Power Up in Data Link Communications |
Does the scan tool communicate with the transfer case shift control module? | Go to Step 3 | Go to Scan Tool Does Not Communicate with Class 2 Device in Data Link Communications | |
Select the Transfer Case Shift Control Module display DTCs function on the scan tool. Does the scan tool display any DTCs? | Go to Step 4 | Go to Symptoms - Transfer Case | |
Does the scan tool display any DTCs which begin with a "U"? | Go to Scan Tool Does Not Communicate with Class 2 Device in Data Link Communications | Go to Step 5 | |
Does the scan tool display DTC P0502 or P0503? | Go to Applicable Powertrain OBD Diagnostic System Check | Go to Symptoms - Transfer Case |