Air Conditioning Switch: Description and Operation

A/C SWITCH STATUS/EVAPORATOR TEMPERATURE STATUS
When the ignition is in the "run" position, the Body Control Module (BCM) monitors the evaporator temperature and the status of the A/C switch. Based on this information, the BCM sends a CCD message to the Powertrain Control Module (PCM) indicating the A/C switch status and the evaporator temperature status.