A/C Pressure Transducer
WARNING: This page is about a different car, the 2015 Lincoln MKT. 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. The PCM prevents the A/C clutch from engaging if the pressure is below a predetermined value for a given ambient temperature.