HVAC Pre-Diagnostic Troubleshooting Procedure

For a complete wiring diagram, refer to appropriate SYSTEM WIRING DIAGRAMS article .

Perform the following steps prior to any diagnostic procedure(s).

Testing should only be performed with the battery fully charged to avoid false diagnosis.
With the scan tool, read Powertrain Control Module (PCM) Diagnostic Trouble Codes (DTCs). If PCM DTCs are present, and perform the appropriate diagnostic procedure(s) before proceeding. Refer to DIAGNOSTIC CODE INDEX (EFH) or DIAGNOSTIC CODE INDEX (EFC) .
Depending on the vehicle configuration, with the scan tool, read Body Control Module (BCM) DTCs. If BCM DTCs are present, perform the appropriate diagnostic procedure(s) in accordance with the service information before proceeding.
With the scan tool, read HVAC DTCs. Record all Stored, Active, and Pending DTC information.
With the scan tool, read the Environmental Data. Use this data to help identify the conditions in which the DTC was set.
Refer to the When Monitored and Set Conditions for this DTC. DTCs can set at ignition on, at start up, or operating under specific conditions.
Using the wiring diagram as a guide, inspect the wiring and connectors related to this circuit and clean/repair as necessary.
Check for controller software updates if applicable. Some conditions can be corrected by upgrading the controller software.
NOTE:
If the controller is updated with new software, with the scan tool, perform a HVAC Actuator Calibration Test.

Check for Service Information Tune-ups or Service Bulletins for any possible causes that may apply.

Did any of the above procedures repair the vehicle?

Yes

Refer to DIAGNOSTIC CODE INDEX and perform the appropriate diagnostic procedure.