Principles of Operation
Auxiliary Brake System - Trailer Brake Control (TBC) Module
Principles of Operation
NOTE: A trailer brake emulator tool is available to verify that the Trailer Brake Control (TBC) module and vehicle wiring are functioning correctly. The trailer emulator requires the trailer tow connector ground and 12 volt trailer tow charge circuit to be connected in order to check the electric brake circuit. Battery Junction Box (BJB) fuse 21 (30A) and the Trailer Tow/Battery Charge Relay must be installed for battery voltage to be supplied to the trailer tow connector. The fuse and relay are supplied as loose-shipped items with the vehicle and may not have been installed during Pre-Delivery Inspection (PDI).
The Trailer Brake Control (TBC) module is an integrated electronic control device designed to provide variable braking power to the electric-actuated drum brakes on a towed trailer (1 to 4 axles only). The braking energy 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 (Trailer Brake Control) module receives information from the stoplamp switch and the PCM. The brake pressure transducer is internal to the ABS module.
The stoplamp switch is mounted on the brake pedal bracket and switches on or off depending on the brake pedal position. The TBC (Trailer Brake Control) module receives the stoplamp switch and the brake torque information over the High Speed Controller Area Network (HS-CAN) from the PCM.
The TBC (Trailer Brake Control) module receives information through the HS-CAN (High Speed Controller Area Network). These inputs are from the PCM, the Instrument Panel Cluster (IPC) and the ABS module. The Body Control Module (BCM) also sends ignition state, park lamp status and illumination dimming level data to the TBC (Trailer Brake Control) module. The information sent from the TBC (Trailer Brake Control) module is passed to the IPC (Instrument Panel Cluster) and is displayed on the message center.
To adjust the gain setting up or down, the TBC (Trailer Brake Control) module faceplate provides the driver with control buttons which determine the maximum power output. The TBC (Trailer Brake Control) module faceplate also provides a manual control lever to manually apply the trailer brakes, independent of the vehicle brakes, to calibrate the gain setting to the specific trailer loading and road conditions. When the manual control lever is activated with a trailer connected to the vehicle, the trailer stoplamps and the vehicle stoplamps (except the center high mount stoplamp) illuminate. If a trailer is not connected and the manual control lever is activated, the vehicle still illuminates the vehicle stoplamps (except the center high mount stoplamp).
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 (Trailer Brake Control) module at start up.
When the ignition key is in the RUN position 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 (Trailer Brake Control) module sends a voltage pulse every 4 seconds to pin 3 of the trailer tow connector to determine whether a trailer is connected to the trailer tow connector.
Instrument Panel Cluster (IPC) Configuration For Trailer Brake Control (TBC) Functionality
The same IPC (Instrument Panel Cluster) is used for vehicles with and without the TBC (Trailer Brake Control) option. TBC (Trailer Brake Control) functionality is enabled or disabled using the scan tool. If the vehicle is equipped with a TBC (Trailer Brake Control) module, but the IPC (Instrument Panel Cluster) was not configured for TBC (Trailer Brake Control), the TBC (Trailer Brake Control) module shuts down, no TBC (Trailer Brake Control) information is displayed in the message center and DTC U2202 sets in the TBC (Trailer Brake Control) module.
If the IPC (Instrument Panel Cluster) is configured for TBC (Trailer Brake Control), but the vehicle is not equipped with a TBC (Trailer Brake Control) module, TRAILER BRAKE MODULE FAULT is displayed in the message center. This symptom could occur if a replacement IPC (Instrument Panel Cluster) was installed, but not configured correctly. For information on the TBC (Trailer Brake Control) programmable parameter, refer to Programmable Parameters below.
Programmable Parameters
The message center displays TBC (Trailer Brake Control) FAULT if it is receiving communications from the TBC (Trailer Brake Control) module, but has not been configured for a trailer brake system. If the message center displays TBC (Trailer Brake Control) FAULT and there are no DTCs stored in the TBC (Trailer Brake Control) module, follow these steps to verify and/or modify the TBC (Trailer Brake Control) module programmable parameter in the Instrument Panel Cluster (IPC).
1. Identify the vehicle using the normal Integrated Diagnostic System (IDS) process.
2. Select Programming and press the check box.
3. Select Module Programming and press the check box.
4. Select Programmable Parameters and press the check box.
5. Select Personality and press the check box.
6. Follow the on-screen directions.
7. NOTE: The scan tool displays either EQUIPPED or NOT EQUIPPED to the left of TBC (Trailer Brake Control) -IPC (Instrument Panel Cluster).
Highlight TBC (Trailer Brake Control) -IPC (Instrument Panel Cluster).
8. If the IPC (Instrument Panel Cluster) needs to be configured for a trailer brake system, choose EQUIPPED and press the check box.
9. Clear DTCs from the TBC (Trailer Brake Control) module, then carry out a self-test on the TBC (Trailer Brake Control) module. Refer to the Trailer Brake Control (TBC) Module DTC Chart for any DTCs retrieved Trailer Brake Control Module.