Achieva L4-144 2.4L DOHC VIN T SFI (1996)
Powertrain Control Module: Description and Operation
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:
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Wide open throttle.
^
High RPM.
^
High power steering loads.
^
Hot engine re-starts.
^
Engine coolant temperature exceeding 125°C.
