A/C Pressure Sensor
The Engine Control Module (ECM) monitors the A/C Refrigerant Pressure Sensor. The A/C Pressure Sensor is embedded in the high-pressure line. Its signal indicates how much load the A/C compressor is putting on the engine, and is one of the factors used by the engine ECM in order to determine the idle air control position for the idle speed. The signal is in voltage, changing proportionally to the A/C pressure from 0V to 5V. Low pressure produces a low-voltage signal and high pressure a high-voltage signal.