Principles of Operation: Notes
WARNING: This page is about a different car, the 2014 Lincoln MKX and 2014 Ford Edge. However, it is still accessible from the selected car via links, so may be relevant.
The Body Control Module (BCM) monitors the input from the stoplamp switch. When the brake pedal is applied, voltage is routed to the BCM , the PCM and (if equipped) the Remote Function Actuator (RFA) module. The BCM then supplies voltage to the stoplamps.
For Edge, the BCM uses a single output to control all of the stoplamps.
For MKX, the BCM uses 3 outputs to control all of the stoplamps and 2 outage circuits to detect a concern with the LH or RH rear stoplamps.