A/C Pressure Transducer
WARNING: This page is about a different car, the 2017 Lincoln Navigator and 2017 Ford Expedition. However, it is still accessible from the selected car via links, so may be relevant.
The PCM monitors the discharge pressure measured by the A/C pressure transducer. As the refrigerant pressure changes, the resistance of the A/C pressure transducer changes. It is not necessary to recover the refrigerant before removing the A/C pressure transducer.
The PCM supplies a 5-volt reference voltage and ground to the A/C pressure transducer. The A/C pressure transducer then sends a voltage to the PCM to indicate the A/C refrigerant pressure.