Calais L4-138 2.3L VIN D FI (1990)
Refrigerant Pressure Sensor / Switch: Description and Operation
A/C PRESSURE SENSOR
The A/C pressure sensor provides a signal to the ECM which indicates varying high side refrigerant pressure between approximately 0.0 psi to 450 psi.
The ECM uses this input to determine A/C compressor load on the engine to help control idle speed with the Idle Air Control (IAC) Valve. The A/C
pressure sensor electrical circuit consist of a 5.0 volt reference line, a ground, and a signal wire to the ECM. The signal is a voltage that varies from
approximately 0.1 volts at 0.0 psi to 4.9 volts at 450 psi or more. A problem with the A/C pressure circuits or sensor should set a Code 66 and will make
the A/C compressor inoperative.
