Normal Operation and Fault Conditions

When the A/C  is requested, the FCIM sends the button press message over the I-CAN  to the IPC. The IPC then sends the button press message to BCM over the HS-CAN  . The BCM then sends the button press message to the HVAC module over the MS-CAN  . Lastly the HVAC module sends an A/C  request message through the MS-CAN  to the BCM and the BCM sends the A/C  request through the HS-CAN  to the PCM.

REFER to Control System Logic 

REFER to Controls and Compressor Cycling 

When an A/C  request is received by the PCM, the A/C  compressor clutch only engages through the A/C  clutch relay if all of the conditions are met:

• The PCM does not detect excessively high or low refrigerant pressure from the A/C  pressure transducer.
• The PCM does not detect excessively high engine coolant temperature.
• The PCM does not detect an ambient air temperature below -1 C (30.2 F).
• The PCM has not detected a WOT condition.
• The HVAC module does not detect an evaporator discharge air temperature below 7.5 C (45.5 F).