Circuit Description
WARNING: This page is about a different car, the 2007 Pontiac G5 Pursuit, 2007 Pontiac G5, and 2007 Chevrolet Cobalt. However, it is still accessible from the selected car via links, so may be relevant.
The engine control module (ECM) or powertrain control module (PCM) monitors the high side refrigerant pressure through the A/C refrigerant pressure sensor. The ECM or PCM supplies a 5-volt reference and a low reference to the sensor. Changes in the A/C refrigerant pressure cause the A/C refrigerant pressure sensor signal to the ECM or PCM to vary. When the pressure is high, the signal voltage is high. When the pressure is low, the signal voltage is low. When pressure is high, the ECM or PCM commands the cooling fans ON. When pressure is too high or too low, the ECM or PCM will not allow the A/C compressor clutch to engage.