Test Description

WARNING: This page is about a different car, the 2003 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.

The numbers below refer to the step numbers on the diagnostic table.

3: Lack of communication may be due to a malfunction of the class 2 serial data circuits. The specified procedure will determine the particular condition.
4: Determine if the Engine Control Module has set DTCs which may affect HVAC operation are present.
5: 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.

Diagnostic System Check - HVAC Systems - Manual

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
3	Turn ON the ignition, with the engine OFF. Attempt to establish communication with the Engine Control Module. Does the scan tool communicate with the Engine Control Module?	Go to Step 4	Go to Scan Tool Does Not Communicate with Class 2 Device in Data Link Communications
4	Select the Engine Control Module display DTCs function on the scan tool. Does the scan tool display any DTCs?	Go to Step 5	Go to Symptoms - HVAC Systems - Manual
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	Go to DIAGNOSTIC SYSTEM CHECK -- ENGINE CONTROLS in Engine Controls - 2.2L (L61) or DIAGNOSTIC SYSTEM CHECK -- ENGINE CONTROLS in Engine Controls - 3.0L (L81)