Trailer Tow
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.
When the vehicle's rear stop/turn or parking lamps are illuminated, voltage is also supplied to a corresponding trailer tow relay (coil side) located in the Battery Junction Box (BJB).
Vehicles not equipped with trailer tow require a Ford authorized accessory kit to add this option. Adding bulbs/lighting to existing circuits can cause the BCM to shut down the circuit and set a DTC due to the unexpected current flow.