Trailer Brake Control
WARNING: This page is about a different car, the 2020 Ford F-150. However, it is still accessible from the selected car via links, so may be relevant.
The trailer brake system uses an Electronic Control Unit (ECU) called the TBM to provide variable braking power to the electric-actuated brakes on a towed trailer (1 to 4 axles only). The braking energy provided to the trailer is modulated with a PWM signal that varies between 0 volt and battery voltage, the higher the duty cycle the more braking power available.