Trailer Brake Control Module: Description and Operation

Auxiliary Brake System - Trailer Brake Control (TBC) Module

Trailer Brake Control System

The trailer brake control system consists of the following components:

- Trailer Brake Control (TBC) module, which is mounted in the center of the instrument panel just below the climate controls
- Brake pressure transducer, which is mounted on the underside of the master cylinder toward the rear of the vehicle
- Brake Pedal Position (BPP) switch, also known as the stoplamp switch, which is mounted on the brake pedal assembly. For information on the stoplamp switch, refer to Lighting and Horns.
- Brake pressure switch, also known as the speed control deactivation switch, which is mounted on the underside of the master cylinder toward the front of the vehicle. For information on the speed control deactivation switch, refer to Fire Suppression System
- ABS module, mounted on the LH side of the vehicle, just forward of the LH shock tower
- PCM, mounted on the RH side of the bulkhead in the engine compartment
- Instrument Cluster (IC)

The TBC module applies the brakes of the trailer for shorter stopping distances and to increase control of the vehicle during braking. The TBC module accomplishes this by monitoring vehicle brake inputs and information from the ABS module and PCM. When the TBC determines that trailer braking is required, a Pulse Width Modulated (PWM) voltage, that is proportional to the brake pressure of the towing vehicle, is sent to the trailer. The trailer brake control system will only work with trailers that are equipped with electric-actuated brakes.

The TBC module has the following driver inputs and outputs:

- Manual slider switch (input)
- Gain buttons (input)
- Gain setting display (output)
- Trailer connectivity icon (output)
- Output bar graph display (output)

The manual slider switch on the TBC module is used to active the trailer brakes independently from the vehicle brakes. The manual slider is used in conjunction with the gain buttons to adjust and set the trailer brakes. When the manual lever is activated with a trailer connected to the vehicle, the trailer stoplamps and the vehicle stoplamps (except the center high mount stoplamp) will illuminate. Activating the manual lever without a trailer connected to the vehicle will still illuminate the vehicle stoplamps (except the center high mount stoplamp).

The gain buttons are used to set the TBC system for specific towing conditions such as trailer load, vehicle load, road conditions and weather. The gain is normally set to provide maximum trailer braking while maintaining trailer stability. For information on setting the trailer brake gain, refer to the Owner's Literature.

The displays are used to provide the driver with TBC system information. Trailer connectivity is provided through the trailer connector icon, the gain setting display provides the driver with the current gain setting and the output bar graph shows the amount of power going to the trailer brakes relative to brake pedal or manual lever input (only if a trailer is connected to the vehicle).

The trailer brake system is normally installed at the assembly plant, however the system can be installed at the dealership. If the system is installed at the dealership, the IC must be reconfigured to communicate with the TBC module.