BRAKE CONTROL SYSTEM


  1. FUNCTION OF MAIN COMPONENTS

    Component Function
    Speed Sensor Detects the wheel speed of each of the 4 wheels.
    Steering Sensor Detects the direction and angle of the steering wheel.
    Brake Pedal Stroke Sensor Assembly Directly detects the extent of the brake pedal stroke operated by the driver.
    Airbag ECU Assembly Yawrate Sensor Detects the vehicle's yaw rate.
    Deceleration Sensor Detects the vehicle's acceleration in the forward, rearward, and lateral directions.
    Stop Light Switch Assembly

    • Detects the brake pedal depression signal.

    • Illuminates the stop lights.*1
    Stop Light Control ECU Assembly*2 Illuminates the stop lights.
    Front Door Courtesy Light Switch Assembly (Driver Side) Detects whether the door is open or closed and sends the information to the skid control ECU.
    Telltale Light Assembly VSC OFF Switch Enables the driver to select normal mode, TRC OFF mode or VSC OFF mode.
    Hazard Warning Signal Switch*3 Sends the switch operation status to the skid control ECU.
    Brake Booster Pump Assembly Pump Motor Supplies brake fluid pressurized by the motor to the accumulator.
    Accumulator Accumulates brake fluid supplied by the pump motor.
    Brake Booster with Master Cylinder Assembly Brake Actuator Changes the brake fluid path based on the signals from the skid control ECU during operation of the normal braking, ABS, EBD, brake assist, TRC, VSC, trailer sway control and hill-start assist control in order to control the fluid pressure that is applied to the wheel cylinders.
    Brake Master Cylinder

    • Generates hydraulic pressure in accordance with the amount of effort applied to the brake pedal by the driver.

    • When a malfunction occurs in the brake system, the brake master cylinder supplies the fluid pressure (which is generated by the brake pedal effort) directly to the wheel cylinders.
    Brake Master Stroke Simulator Cylinder Assembly Generates a pedal stroke during braking in accordance with the driver's pedal effort.
    Skid Control ECU

    • Monitors the driving conditions of the vehicle in accordance with the signals received from the sensors and through cooperative control with the hybrid vehicle control ECU and power steering ECU calculates the required amount of brake force, and controls the brake actuator.

    • Judges the vehicle driving condition based on signals from each sensor, and controls ABS, EBD, brake assist, TRC, VSC, trailer sway control and hill-start assist control.

    • Operates the brake booster pump assembly to control accumulator pressure based on accumulator pressure sensor signals.
    Brake Master Cylinder Reservoir Assembly Brake Fluid Level Warning Switch Detects the low brake fluid level.
    ECM Outputs signals such as the throttle position signal and engine speed signal to the skid control ECU.
    Hybrid Vehicle Control ECU

    • Actuates the regenerative braking on receiving signals from the skid control ECU.

    • Sends the actual regenerative brake control value to the skid control ECU.

    • Controls the motive force based on an output control request signal received from the skid control ECU while the TRC, VSC or trailer sway control is operating.
    Main Body ECU (Multiplex Network Body ECU) Outputs signals such as the parking brake signal to the skid control ECU.
    Power Steering ECU Assembly Controls the steering assist torque based on the signals received from the skid control ECU.
    Driving Support ECU Assembly*4 Makes a request for brake control to the skid control ECU.
    Combination Meter Assembly Brake Warning Light / Red (Malfunction)

    • Illuminates to alert the driver that the skid control ECU detects the malfunction in the apportioning of the brake force.

    • Illuminates to inform the driver when the parking brake is on or the brake fluid is low.
    Brake Warning Light / Yellow (Minor Malfunction) Illuminates to alert the driver that a minor malfunction which does not affect the braking force has occurred in the brake system.
    ABS Warning Light Illuminates to alert the driver when the skid control ECU detects a malfunction in the ABS, EBD or brake assist.
    Slip Indicator Light

    • Blinks to inform the driver when the ABS, TRC, VSC or trailer sway control is operational.

    • Illuminates to alert the driver when the skid control ECU detects a malfunction in the TRC, VSC, trailer sway control or hill-start assist control.
    VSC OFF Indicator Light Illuminates to inform the driver when VSC OFF mode is selected.
    Multi-information Display

    • Displays the information message when TRC OFF mode is selected.

    • Displays the warning message when the skid control ECU detects a malfunction in the system.
    Master Warning Light Illuminates when the warning message is displayed in the multi-information display.
    Buzzer Sounds together with a message display on the multi-information display during a system malfunction.

    • *1: RHD models

    • *2: LHD models

    • *3: Models with emergency brake signal

    • *4: Models with pre-crash safety system

  2. OPERATING CONDITION


    1. Hill-start Assist Control


      1. The hill-start assist control operates when all of the following conditions have been met:

        Control Start Conditions

        • The shift lever is in any position other than P or N (when taking off or reversing on an uphill slope).

        • The vehicle is at a standstill.

        • The accelerator pedal is not depressed.

        • The parking brake is not applied.

      2. If any one of the below conditions is met during hill-start assist control operation, hill-start assist control will be canceled.

        Control Cancelation Conditions

        • The driver moves the shift lever to P or N.

        • The driver depresses the accelerator pedal.

        • The parking brake is applied.

        • 2 seconds have elapsed since the hill-start assist control operated.

  3. SYSTEM CONTROL


    1. The brake control system (ABS, EBD, brake assist, TRC, VSC, steering cooperative control, hill-start assist control and trailer sway control) has the following controls:

      Control Outline
      Anti-lock Brake System (ABS) The ABS helps prevent the wheels from locking when the brakes are applied firmly or when braking on a slippery surface.
      Electronic Brake Force Distribution (EBD) The EBD control utilizes the ABS, achieving proper brake force distribution between the front and rear wheels in accordance with the driving conditions. In addition, during braking while cornering, the EBD also controls the brake forces of the right and left wheels, helping maintain vehicle behavior.
      Brake Assist The primary purpose of brake assist is to provide an auxiliary brake force to assist a driver who cannot generate a large brake force during emergency braking, helping ensure the vehicle's braking performance.
      Traction Control (TRC) The TRC helps restrain the slippage of the drive wheels if the driver depresses the accelerator pedal excessively when starting off or while accelerating on a slippery surface.
      Vehicle Stability Control (VSC) The VSC helps restrain sideways slippage of the vehicle during a strong front wheel skid or strong rear wheel skid, which may occur while cornering.
      Steering Cooperative Control Effects cooperative control with the power steering ECU in order to provide steering assist in accordance with the operating conditions of the vehicle.
      Hill-start Assist Control When starting uphill, this control maintains the brake hydraulic pressure on all 4 wheels in order to momentarily prevent the vehicle from descending backward.
      Trailer Sway Control If the tongue load is not properly adjusted while towing a trailer, trailer sway may be caused due to crosswinds, bumpy roads, steering operation, etc. Trailer sway control detects sway and regulates the brake of each wheel and the motive force output in order to suppress trailer sway.

  4. FAIL-SAFE


    1. In the event of a malfunction of the ABS, the skid control ECU can control the EBD if the EBD works properly.

    2. In the event of a malfunction of the ABS and/or EBD, the skid control ECU will illuminate the brake warning lights to alert the driver of the malfunction and will disable brake control system operation.

    3. In the event of a malfunction of the TRC, VSC and/or trailer sway control, the skid control ECU will disable the TRC, VSC and trailer sway control operation.

    4. If a communication malfunction occurs between the skid control ECU and the steering sensor, airbag sensor assembly (yawrate sensor or deceleration sensor) or hybrid vehicle control ECU, the skid control ECU will disable the TRC, VSC and trailer sway control operation.

    5. When the hybrid vehicle control ECU detects a Diagnostic Trouble Code (DTC), it will disable the TRC, VSC and trailer sway control operation.

  5. DIAGNOSIS


    1. If the skid control ECU detects a malfunction in the brake control system (ABS, EBD, brake assist, TRC, VSC and steering cooperative control, hill-start assist control and trailer sway control), then the ABS warning light, brake warning light (red or yellow indicator) or slip indicator light will illuminate either individually or as a group according to the function in which the malfunction has been detected, to alert the driver of the malfunction.

    2. At the same time, a Diagnostic Trouble Code (DTC) will be stored in memory.

    3. This system has a sensor signal check (test mode) function.

    4. For details of DTCs and the check function, refer to the Repair Manual.