A/C Signal: Description and Operation

PURPOSE
The Air Conditioning (A/C) refrigerant pressure sensor provides a signal to the Powertrain Control Module (PCM) which indicates varying high side refrigerant pressure between approximately 0 psi and 450 psi.

OPERATION
The PCM 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 refrigerant pressure sensor electrical circuit consists of a 5.0 volt reference line, a ground line, and a signal line to the PCM. The signal is a voltage that varies from approximately 0.1 volt at 0 psi, to 4.9 volts at 450 psi or more. A problem in the A/C refrigerant pressure circuits or sensor should set a Diagnostic Trouble Code (DTC) 66 or 70 and will make the A/C compressor clutch inoperative. A faulty ground circuit at the sensor will result in a fixed high pressure value.

Refer to Code 66 A/C Pressure Sensor (Low) Circuit or Code 70 A/C Pressure Sensor (High) Circuit for diagnosis of the A/C refrigerant pressure sensor. [1][2]DTC 70