A/C Pressure Sensor
WARNING: This page is about a different car, the 2003 Saturn LW200 and 2003 Saturn L200. However, it is still accessible from the selected car via links, so may be relevant.
Some models are equipped with an air conditioner pressure sensor which is used to inform PCM of A/C system pressure. PCM uses this signal to determine A/C compressor load on the engine to control idle speed with IAC valve. Failure in A/C pressure sensor circuit or with A/C pressure sensor should set a related diagnostic trouble code and A/C compressor clutch will become inoperative. A fixed high pressure value will exist if the ground circuit to sensor is faulty.