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 on the instrument panel to the right of the steering wheel
- For vehicles equipped with a TorqShift transmission, a brake pressure transducer is mounted on the underside of the master cylinder toward the rear of the vehicle and can be serviced separately from the master cylinder
- For vehicles equipped with Roll Stability Control (RSC(R)), a brake pressure transducer is internal to the Hydraulic Control Unit (HCU) and is serviced with the HCU. Refer to Vehicle Dynamic Systems Service and Repair
- 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, under the brake master cylinder
- PCM, mounted on the LH 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:

- Manual slider switch (input)
- Gain buttons (input)

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 message center in the IC is used to provide the driver with TBC system information in regards to trailer gain setting, trailer brake output and trailer connectivity.

- TBC GAIN = XX.X NO TRAILER will be displayed if there is no trailer connected to the 7-pin trailer tow connector and a gain setting is input into the TBC module. Gain is input into the module in increments of 0.5 up to a maximum of 10.0.
- TBC GAIN = XX.X OUTPUT = ////// will be displayed if there is a trailer connected to the 7-pin trailer tow connector and a gain setting is input into the TBC module or the brake pedal is applied or the manual slider switch is activated. One bar indicates the least amount of output while 6 bars indicates the maximum amount of output to the trailer brakes.
- TRAILER CONNECTED will be displayed when a trailer is correctly connected to the 7-pin trailer tow connector.
- TRAILER DISCONNECTED will be displayed if a trailer is disconnected from the 7-pin trailer tow connector (intentionally or unintentionally) during the same ignition key cycle in which a successful connection was detected by the TBC module. This message will also be displayed if there is a wiring fault in the vehicle or trailer, or if the manual slider switch is activated without a trailer connected to the vehicle.