Seatbelt Tension Sensor (BTS)
WARNING: This page is about a different car, the 2018 Ford Edge. However, it is still accessible from the selected car via links, so may be relevant.
The safety Belt Tension Sensor (BTS) is a 3-wire Hall-effect sensor that is part of the front passenger seatbelt buckle and cannot be serviced separately from the front passenger seatbelt buckle assembly.