Test Description
The number(s) below refer to the step number(s) on the diagnostic table.
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Lack of communication 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 will determine the particular condition.
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The presence of DTCs indicates that the transfer case shift control module has detected a fault. Go to symptoms for other concerns.
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The presence of DTCs which begin with "U" indicate some other module is not communicating. The specified procedure will compile all the available information before tests are performed.
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Vehicle speed is provided to the transfer case shift control module via Class 2. Perform the diagnostics for powertrain DTCs P0502 and 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 Diagnostic System Check - Engine Controls in Engine Controls - 6.6L or Diagnostic System Check - Engine Controls in Engine Controls - 8.1 L |
