Principles of Operation

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 volts and battery voltage, the higher the duty cycle the more braking power available.

The TBC module receives information through the controller area network (CAN). These inputs are from the powertrain control module (PCM), instrument cluster and the anti-lock brake system (ABS) module. The information sent out from the TBC module is through the CAN and is displayed on the instrument cluster message center.

The TBC module faceplate provides the driver with control buttons to adjust the gain setting UP or DO, which determines the maximum power output sent to the 7-pin connector. The TBC module faceplate also provides a manual control lever to manually apply the trailer brakes independent of the vehicle brakes in order to calibrate the gain setting to the specific trailer loading and road conditions. Note that when the manual control is activated, both the vehicle and the trailer brake lamps illuminate. If there is no trailer connected and the manual control lever is activated, the vehicle brake lamps still illuminate. The TBC module faceplate displays the gain setting and relative trailer braking power during a braking event. The TBC module also has an illuminated red or green trailer icon that displays trailer connectivity status to the driver.

The TBC module is operating correctly if these conditions are met. Turn the key to the ON position (no trailer connected). The TBC module LEDs should not be lit with no pedal or manual input. Verify the slider is not stuck, then set the gain to 10 and slide the manual lever to the left and make sure the LEDs light up and that the message center says TRAILER DISCONNECTED or CHECK TRAILER. With the vehicle stationary there should be greater than 10-12 volts supplied to the trailer tow C4099-3 circuit 43 (DB). If these conditions are met the system is considered to be operating normally.