PINPOINT TEST M : The Air Conditioning (A/C) Is Inoperative: Notes

Refer to AUTOMATIC CLIMATE CONTROL SYSTEM for schematic and connector information.

Normal Operation and Fault Conditions 

When the A/C is requested, the FCIM sends the 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 CLIMATE CONTROL - DATC , Control System Logic

Refer to CLIMATE CONTROL - DATC , 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 these 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 0°C (32°F).

Possible Sources 

• Fuse
• Wiring, terminals or connectors
• A/C system discharged/low charge
• PCM
• HVAC module
• FCIM
• Evaporator temperature sensor
• A/C pressure transducer
• A/C compressor
• A/C clutch relay
• A/C compressor clutch air gap

Visual Inspection and Diagnostic Pre-checks 

• Inspect the BJB fuse 62 (10A).
• Inspect the A/C clutch relay.
• Inspect for A/C system discharged/low charge.