Auxiliary Brake System - Trailer Brake Control (TBC) Module: Overview

The trailer brake system uses an ECU  called the TBC  module to provide variable braking power to the electric actuated drum 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.