Trailer Brake Control Module: Description and Operation
Auxiliary Brake System - Trailer Brake Control (TBC) Module
Trailer Brake Control (TBC) System
The Trailer Brake Control (TBC) system consists of the following components:
- TBC module, which is mounted on the instrument panel to the right of the steering wheel
- Brake pressure transducer, which is internal to the Hydraulic Control Unit (HCU) and is serviced with the HCU.
- Brake Pedal Position (BPP) switch, also know as the stoplamp switch and is mounted on the brake pedal assembly
- 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)
- Vacuum fluorescent display (output)
- gain setting
- trailer connectivity icon
- output bar graph
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 vacuum fluorescent display is 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 but only if the vehicle is equipped with the trailer tow option. This option can be confirmed by verifying the presence of both the 4-pin and the 7-pin connectors at the rear of the vehicle as well as a receiver hitch. If the vehicle is not equipped with these 3 items, then it is not equipped with trailer tow and cannot have the factory TBC system installed.
On those vehicles equipped with the trailer tow option, the electrical connector for the TBC module is attached to the back of the coin bin/storage tray. If the system is installed at the dealership, the TBC module will be installed in place of the coin bin/storage tray and the IC must be configured to communicate with the TBC module. Refer to the Wiring Diagram Set 95 Trailer/Camper Adapter and vehicle level Component Location Views for connector and wiring information. Refer to Programmable Parameters in the Diagnosis and Testing for information on IC configuration. Diagrams By Number Programming and Relearning