The A/C compressor clutch is controlled by the PCM. The HVAC controller sends the A/C request to the PCM, and through the Class II serial data circuit to the PCM with CJ2. 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 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 Compressor Controls Circuit Description for C60 and CJ3 HVAC System-Manual or HVAC Compressor Controls Circuit Description for CJ2 in HVAC System-Automatic.