Test Description
The numbers below refer to the step numbers 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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Determine if the Powertrain Control Module has set DTCs which may affect HVAC operation are present.
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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.
Step | Action | Yes | No |
|---|---|---|---|
1 | Did you review A Diagnostic Starting Point - Heating, Ventilation and Air Conditioning? | Go to Step 2 | Go to Diagnostic Starting Point - Heating, Ventilation and Air Conditioning in Heating, Ventilation and Air Conditioning |
2 | Install a scan tool. Does the scan tool power up? | Go to Step 3 | Go to Scan Tool Does Not Power Up in Data Link Communications |
Does the scan tool communicate with the Powertrain Control Module? | Go to Step 4 | Go to Scan Tool Does Not Communicate with Class 2 Device in Data Link Communications | |
Select the Powertrain Control Module display DTCs function on the scan tool. Does the scan tool display any DTCs? | Go to Step 5 | ||
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 6 | |
6 | Does the scan tool display any DTCs which begin with a P that are associated with the HVAC system? | Go to Diagnostic Trouble Code (DTC) List in Engine Cooling | Go to Diagnostic System Check - Engine Controls in Engine Controls - 4.3L |
