PATS Transceiver
WARNING: This page is about a different car, the 2018 Ford Focus. However, it is still accessible from the selected car via links, so may be relevant.
The PATS transceiver reads any key placed in the ignition lock cylinder. When the ignition changes to RUN or START, the BCM activates the PATS transceiver. Once the transceiver activates, it activates the key transponder in the ignition and receives the key data. Once the transceiver receives the key data, it sends the data to the BCM.