BRAKE CONTROL SYSTEM


  1. FUNCTION OF MAIN COMPONENTS

    Component Function
    Speed Sensor Detects the wheel speed of each of the 4 wheels.
    Spiral Cable with Sensor Sub-assembly 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.
    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.
    VSC OFF Switch Enables the driver to select normal mode, TRC OFF mode or VSC OFF mode.
    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 and hill-start assist control in order to control the fluid pressure that is applied to the wheel cylinders.
    Hydraulic Brake Booster (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 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.
    Main Body ECU (Multiplex Network Body ECU) Transmits the parking brake signal to the skid control ECU.
    EV 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 or VSC is operating.
    Parking Brake Switch Assembly Detects the parking brake pedal status.
    Power Steering ECU Controls the steering assist torque based on the signals received from the skid control ECU.
    Driving Support ECU 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 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 or VSC is operational.

    • Illuminates to alert the driver when the skid control ECU detects a malfunction in the TRC, VSC 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.
    Multi Buzzer This buzzer sounds continuously to inform the driver when there is a malfunction in the hydraulic pressure circuit or a failure in the power supply.
    Parking Brake Warning Light Illuminates to alert the driver while the parking brake is applied.

  2. SYSTEM CONTROL


    1. The brake control system 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.
      VSC+ 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.
      Radar Cruise Control Brake When the driving support ECU assembly determines that a large amount of deceleration is required based on the distance to the preceding vehicle and the relative vehicle speed during the dynamic radar cruise control system operation, the skid control ECU operates the brake system according to the signal from the driving support ECU assembly.
      Pre-crash Brake When the driving support ECU assembly determines that the possibility of a collision is high or an unavoidable collision condition exists, the skid control ECU activates the pre-crash brake assist or the pre-crash brake according to the signal from the driving support ECU assembly.

  3. 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 and/or VSC, the skid control ECU will disable the TRC and VSC operation.

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

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

  4. DIAGNOSIS


    1. If the skid control ECU detects a malfunction in the brake control system (ABS, EBD, brake assist, TRC, VSC, VSC+ and hill-start assist 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.