Parking Brake Position Switch
WARNING: This page is about a different car, the 2013 Ford Explorer. However, it is still accessible from the selected car via links, so may be relevant.
The parking brake position switch is hardwired to the BCM through a signal and return circuit. The BCM provides a battery reference voltage on the signal circuit. The return circuit is grounded internally in the BCM . When the parking brake is not applied, the parking brake position switch is open. When the parking brake is applied, the parking brake position switch closes, pulling the reference voltage low.