Principles Of Operation

Auxiliary Brake System - Trailer Brake Control (TBC) Module







Principles of Operation

The Trailer Brake Control (TBC) module is an integrated electronic control device that is designed to provide variable braking power to the electric-actuated drum brakes on a towed trailer (1 to 4 axles only). The braking energy that is provided to the trailer is varied with a Pulse Width Modulated (PWM) signal that switches between 0 volt and battery voltage, the higher the duty cycle the more braking power available.

The TBC module receives information from 3 different brake pedal inputs: the Brake Pedal Position (BPP) switch, the brake pressure switch (also known as the speed control deactivation switch) and the brake pressure transducer.

The BPP switch is mounted on the brake pedal bracket and switches on or off depending on the brake pedal position. The brake pressure switch is mounted on the bottom of the master cylinder near the front and switches on or off depending on the pressure applied on the brake pedal. The TBC module receives both the BPP and the brake pressure switch information over the High Speed Controller Area Network (HS-CAN) bus from the PCM.

The brake pressure transducer is mounted on the bottom of the master cylinder near the rear and sends a variable voltage to the TBC module depending on the pressure applied to the brake pedal. The TBC module receives this information directly from the pressure transducer.

The TBC module receives information through the HS-CAN bus. These inputs are from the PCM, the Instrument Cluster (IC) and the ABS module. The information sent out from the TBC module is through the IC and is displayed on the message center.

To adjust the gain setting up or down, the TBC module faceplate provides the driver with control buttons which determine the maximum power output sent to the 14-pin connector. The TBC module faceplate also provides a manual control lever to manually apply the trailer brakes, independent of the vehicle brakes, to calibrate the gain setting to the specific trailer loading and road conditions. Note that when the manual control is activated, both the center high-mounted stoplamp and the trailer brake lamps illuminate. If a trailer is not connected and the manual control lever is activated, the vehicle center high-mounted stoplamp will still illuminate.


Instrument Cluster (IC) Configuration For Trailer Brake Control (TBC) Functionality

The same IC is used for vehicles with and without the TBC option. TBC functionality is enabled or disabled using the scan tool. If the vehicle is equipped with a TBC module, but the IC was not configured for TBC, the TBC module will shut down, no TBC information will be displayed in the message center and DTC U2202 will set in the TBC module.

If the IC is configured for TBC, but the vehicle is not equipped with a TBC module, TRAILER BRAKE MODULE FAULT will be displayed in the message center. This symptom could occur if a replacement IC was installed, but not configured correctly. For information on the TBC programmable parameter, refer to Programmable Parameters in Inspection and Verification. Programming and Relearning