Module, Integrated Trailer Brake (ITBM): Operation
The Body Control Module (BCM) is responsible for providing the ITBM with its configuration parameters.
Trailer Brake Style Selection
The ITBM controls the trailer brakes during vehicle braking (driver braking or autonomous braking), hill start assist, trailer sway event and Adaptive Cruise Control (ACC) or Forward Collision Warning (FCW) events. ITBM is available only after ignition start and in forward or reverse gear. ITBM warns in case of trailer brake fault.
The customer can select the trailer brake styles of either electric brakes or electric over hydraulic brakes depending on the size and the type of trailer. The ITBM sends the trailer brake style feedback signal over the Controller Area Network (CAN) bus to the Instrument Panel Cluster (IPC).
Trailer Type Selection
The ITBM stores up to four individual trailer settings and once the customer selects the trailer type, the ITBM sends the selection to the radio for display.
Gain Switch Setting
The customer is able to set a gain value depending on the trailer output brake required. Gain value can be changed by two hardwire signals, Gain + and Gain -. The ITBM sends the gain value by CAN signal to the IPC when it is set and when it is changed.
The IPC triggers its trailer tow menu when it receives a gain signal from the ITBM.
Manual Lever Switch
The manual lever is a squeeze switch and when pressed, a Pulse Width Modulated (PWM) output signal will be proportional to the deflection on the lever. Manual lever hardwire information is sent to the ITBM.
Trailer Brake Lamp
The ITBM requests brake lamp activation and deactivation when the manual lever switch is active via a CAN bus signal.
Trailer Brake Output: Automatic Braking
Driver Request - When the brake pedal is pressed, the trailer brake sends a PWM output signal that includes a value proportional brake torque PWM signal as well as the gain value and the trailer type selected by the customer. The ITBM determine the proportional brake torque value from the Automatic Braking System (ABS) module and will also use the ABS vehicle speed CAN signal to determine the brake output.
During automatic braking events, the ABS module outputs a signal that the trailer brakes use to determine their output. For Hill Start Assist (HSA) events, this is a calibrated value that determines the trailer brake output response.
Trailer Brake Output: Manual Braking
When the manual lever switch is active, the trailer output is proportional to gain, trailer settings and the position of the lever switch.
Trailer Brake: Backup Algorithm
The backup algorithm is used as a backup for automatic braking. If the ABS module torque signal is not available, the ITBM determines if the vehicle is braking using the accelerometer values instead. The trailer output PWM values are proportional to gain, trailer settings and accelerometer value.
Trailer Travel Distance
Trailer trip distance is accumulated by the ITBM after the trailer is connected to the vehicle. The odometer information is received by the ITBM by an output signal from the IPC. The ITBM reads the odometer information and accumulates the trailer travel distance. The ITBM saves the trailer travel distance across key cycles and also sends the trailer trip distance to the IPC over the CAN bus. The IPC receives the signal from the ITBM and will display the trailer trip distance in the cluster.
Trailer Faults
If the ITBM detects a diagnostic failure mode with the switch bank or the system itself, the ITBM will set the appropriate Diagnostic Trouble Code (DTC) and then automatic braking, Manual braking may still be available which is dictated by the detected fault type.