PCM Outputs

PCM CONTROLLED AIR CONDITIONING
The A/C compressor clutch is controlled by the Powertrain Control Module (PCM). 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.

The PCM controlled air conditioning system uses a variable displacement compressor referred to as a V-5 compressor. The V-5 compressor meets the A/C requirements without cycling.

The PCM controlled air conditioning system consists of an A/C compressor clutch relay, an A/C compressor clutch and an A/C refrigerant pressure sensor. The Instrument Panel Cluster (IPC) and the A/C select switch also have input the PCM through the Universally Asynchronous Receiving/Transmitting (UART) serial data circuit.

The A/C refrigerant pressure sensor is used to indicate high side pressures. The PCM uses this information to control the cooling fan operation, the A/C compressor clutch operation and the idle speed. A fault in the A/C refrigerant pressure sensor circuit will set a DTC P0530. This will cause the PCM to disable the A/C compressor clutch compressor. The PCM determines high and low pressures in the A/C system by the voltage signal it receives from the A/C refrigerant pressure sensor. This allows the PCM to protect the A/C system from excessively high and low pressures. If the A/C refrigerant pressure sensor voltage exceeds about 4.7 Volts, indicating pressure of 428 psi, the PCM will disable the A/C compressor clutch. The A/C compressor clutch will remain disabled until the A/C refrigerant pressure sensor voltage falls below 1.98 Volts, indicating about 170 psi. The PCM will temporarily disable the A/C compressor clutch during the following conditions:
^ Wide open throttle.
^ High RPM.
^ High power steering loads.
^ Hot engine re-starts.
^ Engine coolant temperature exceeding 125°C.