Principles of Operation: Notes

WARNING: This page is about a different car, the 2009 Ford RV Cutaway, 2009 Ford Econoline, 2009 Ford E450 Super Duty, and 2009 Ford Cutaway. However, it is still accessible from the selected car via links, so may be relevant.

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) voltage that switches between 0 volt and battery voltage, the higher the duty cycle the more braking power available.

The TBC module receives vehicle braking information from 2-3 different inputs depending on vehicle options. The first input is the Brake Pedal Position (BPP) switch (also known as the stoplamp switch). The BPP switch provides the PCM with the current brake pedal position (pressed or released), this information is sent to the PCM as a voltage input and is then transmitted to the TBC module over the High Speed Controller Area Network (HS-CAN) bus. The second (and third) input is the brake pressure transducer. On vehicles equipped with a TorqShift transmission, the transducer is mounted on the master cylinder and on vehicles equipped with Roll Stability Control (RSC®), the transducer is inside the Hydraulic Control Unit (HCU). Regardless of mounting position, both transducers produce a signal that varies with the force applied to the brake pedal. Once the PCM (for master cylinder mounted) and/or the ABS module (for HCU mounted) receives the signal, it is then transmitted to the TBC module over the HS-CAN bus.

The TBC module also receives additional vehicle information over the HS-CAN bus. These inputs are from the PCM, the Instrument Cluster (IC) and the ABS module. These inputs are then used to determine the amount of braking power required for the trailer. The TBC module will also transmit information to the ABS module and the IC in regards to trailer connectivity and current TBC system status. System status information that is sent to the IC will be displayed in the IC message center to alert the driver of trailer status and any potential concerns.

TBC module output to the trailer can be adjusted by the driver through the use of the manual slide lever and the 2 gain buttons. Pressing a gain button with a trailer connected to the vehicle will adjust the TBC output to the trailer brakes to set the maximum assistance while making sure the trailer wheels do not lock while braking. The maximum setting is 10.0 and the minimum setting is 0.0. The manual control lever is used to manually apply the trailer brakes, independent of the vehicle brakes, in order to calibrate the trailer gain setting to the specific trailer loading and road conditions. For information on setting trailer gain, refer to the owner's manual or literature.

The IC message center displays the trailer connectivity status as well as gain setting (number display) and relative trailer braking power (output bar graph) during a braking event. When a successful trailer connection is detected by the TBC module, the message center will display TRAILER CONNECTED. If the electrical connection to the trailer is lost or disconnected during the same ignition cycle, the message center will display TRAILER DISCONNECTED.