Circuit Description
WARNING: This page is about a different car, the 2007 Hummer H2. However, it is still accessible from the selected car via links, so may be relevant.
The powertrain control module (PCM) monitors the high side refrigerant pressure via an A/C refrigerant pressure sensor. When the pressure is high, the signal voltage is high. When the pressure is low, the signal voltage is low. When pressure is too high, the PCM will not allow the A/C compressor clutch to engage.