Trailer Brake Control System

WARNING: This page is about a different car, the 2017 Lincoln Navigator and 2017 Ford Expedition. However, it is still accessible from the selected car via links, so may be relevant.

The gain buttons 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 manual slider switch on the TBC module activates 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 slider switch is activated with a trailer connected to the vehicle, the trailer stoplamps and the vehicle stoplamps illuminate. Activating the manual slider switch without a trailer connected to the vehicle illuminates the vehicle stoplamps except the center high-mount stop lamp.

Once the driver sets the desired gain, the TBC module monitors the HS-CAN messages from the PCM and ABS module as well as the manual slider switch input to determine if trailer braking is necessary. If trailer braking is necessary, the TBC module sends a PWM signal to the trailer to activate the trailer brakes.

Trailer Brake Control (TBC) Module Wake Up

NOTE: These conditions require that a trailer not be connected to the trailer tow connector.

The following conditions describe the normal operation of the TBC module at start up.

When the ignition is set to ON and the manual lever is set all the way to the left with a gain of 10, the message center should display TRAILER DISCONNECTED. At the same time, with the vehicle stationary, battery voltage should be present at pin 3 of the trailer tow connector.

When not braking, the TBC module sends a voltage pulse every 4 seconds to pin 3 of the trailer tow connector for TBC module output circuit diagnostics.

TBC System Message Center Messages

The TBC module continually monitors the trailer brake system operation and trailer connectivity. The TBC module sends system operation information such as gain setting and relative braking power to the IPC along the HS-CAN. If a system fault or a trailer connectivity issue is detected, the TBC module sends a message to the IPC along the HS-CAN. When the IPC receives a message from the TBC module, one or more of the following messages is displayed on the message center:

NO TRAILER - This message is displayed whenever the ignition is cycled from OFF to ON without a trailer connected to the 7-pin trailer tow connector.
OUTPUT = / / / / / / - When the vehicle brake pedal is applied or when the manual slider switch is activated, bar indicators illuminate in the message center to indicate the amount of power going to the trailer brakes relative to the brake pedal or manual slider switch input. One bar indicates the least amount of output while 6 bars indicates the maximum output.
TBC GAIN = XX.X - This message shows the current gain setting for the trailer with a trailer connected to the 7-pin trailer tow connector.
TBC FAULT - The message is displayed when the IPC is receiving communications from the TBC module, but has not been configured for a trailer brake system. If the message center displays TBC FAULT and there are no DTCs stored in the TBC module, verify the IPC is programmed for trailer brakes. Refer to for information on module programmable parameters.
TRAILER BRAKE MODULE FAULT - This message is displayed and accompanied by a single chime when a fault is detected by the TBC module. A DTC is stored in the TBC module when this message is displayed.
TRAILER CONNECTED - This message is displayed when the correct type of trailer is connected to the 7-pin trailer tow connector during a given ignition cycle.
TRAILER DISCONNECTED - This message is displayed when the correct type of trailer is connected to the 7-pin trailer tow connector and then disconnected during the same ignition cycle or if the manual slider switch is actuated without a trailer connected to the vehicle. This message is also displayed if the 7-pin trailer connector becomes disconnected while driving or if an intermittent open circuit occurs in the vehicle wiring from the TBC module to the 7-pin trailer connector or in the trailer wiring.
WIRING FAULT ON TRAILER - This message is displayed when the TBC module output circuit is shorted to ground or shorted to voltage. A DTC is set in the TBC module indicating which circuit fault was observed. It is important to determine if a trailer was connected when this message was displayed. If this message is only observed with a trailer connected, the concern is related to the trailer wiring and not the vehicle. If this message is observed along with a single chime and without a trailer connected, the concern is with the vehicle wiring from the TBC module to the 7-pin trailer connector.