The A/C compressor clutch is controlled by the PCM.The HVAC controller sends the A/C request to the PCM through the Class ll serial data circuit.This allows the PCM to manage idle quality, improve wide open throttle performance, and to protect the A/C system from excessively high and low pressures. In addition the PCM will command the cooling fans on during A/C operation. The PCM monitors the A/C compressor refrigerant pressure. When the A/C refrigerant pressure, and engine operating conditions are within specific calibrated ranges the PCM will enable the A/C compressor relay. This is accomplished by providing a ground path for the A/C relay coil within the PCM. When the A/C compressor relay is enabled battery voltage is supplied to the compressor clutch coil. Refer to HVAC System HVAC Compressor Controls Circuit Description for C60 and CJ4.