BRAKE CONTROL SYSTEM


  1. FUNCTION OF MAIN COMPONENTS

    Component Function
    Speed Sensor Detects the wheel speed of each of the 4 wheels.
    Yawrate Sensor

    • Detects the vehicle's longitudinal and lateral acceleration.

    • Detects the vehicle's yaw rate.
    Steering Sensor Detects the direction and angle of the steering wheel.
    Stop Light Switch Assembly Detects the brake pedal depressing signal.
    Brake Pedal Stroke Sensor Assembly Directly detects the extent of the brake pedal stroke operated by the driver.
    No. 3 Semiconductor Power Integration ECU Illuminates or flashes the stop lights according to signals from the stop light switch assembly and skid control ECU assembly.
    No. 2 Engine Room Relay Block Assembly No. 1 and No. 2 ABS MTR Relay Controlled by the skid control ECU assembly to supply power to the pump motor. Normally, the No. 1 ABS MTR relay is used, but when a malfunction occurs in the No. 1 ABS MTR relay, the No. 2 ABS MTR relay is used.
    Satellite Switch Set VSC OFF Switch Enables the driver to select "Normal Mode", "TRC OFF Mode" or "VSC OFF Mode".
    Brake Hold Switch Switches the brake hold on and off.
    Hazard Warning Signal Switch Assembly Switches the Hazard Warning Signal on and off.
    Front Door Courtesy Lamp Switch Assembly LH Detects whether the door is open or closed and sends the information to the skid control ECU.
    Brake Control Power Supply Assembly

    • An auxiliary power supply to provide stable electrical power to the brake system.

    • When the voltage of the auxiliary battery is low, the brake control power supply assembly supplements the supply of power to the brake system by providing the electric charge that is stored in the unit.
    Brake Master Cylinder Reservoir Assembly Brake Fluid Level Warning Switch Detects the low brake fluid level.
    Brake Booster with Accumulator Pump Assembly Pump Motor Supplies brake fluid pressurized by the motor to the accumulator.
    Accumulator Accumulates brake fluid supplied by the pump motor.
    Brake Actuator Assembly Accumulator Pressure Sensor Detects the accumulator pressure.
    Master Cylinder Pressure Sensor Detects the master cylinder pressure.
    Wheel Cylinder Pressure Sensor Detects the wheel cylinder pressure of each of the 4 wheels.
    Switching Solenoid Valve Switches the fluid path to shut off or release the hydraulic pressure from the master cylinder.
    Linear Solenoid Valve Switches the fluid path to increase or decrease the hydraulic pressure of the wheel cylinder.
    Skid Control ECU Assembly

    • Operates the brake actuator assembly according to signals from sensors and ECUs to control the brake hydraulic pressure of each wheel.

    • Performs comprehensive control in accordance with regenerative brake cooperative control and Vehicle Dynamics Integrated Management (VDIM) according to communication with each ECU.
    Hybrid Vehicle Control ECU Assembly

    • Controls the brake force of regenerative braking during regenerative brake cooperative control according to communication with the skid control ECU assembly.

    • Controls the motive force when TRC and VSC are operating according to communication with the skid control ECU.

    • Sends the accelerator pedal position signal, shift position signal and brake request signal to the skid control ECU.
    Parking Brake ECU Assembly Operates the parking brake actuator assembly according to signals from the skid control ECU assembly.
    Power Steering ECU with Motor Assembly Power Steering ECU Controls the steering assist torque based on the signals received from the skid control ECU assembly.
    Front Steering Control ECU*1

    • Controls the turning angle of the front wheels based on the signals received from the skid control ECU assembly.

    • Operates the steering actuator assembly to control the turning angle of the front wheels.
    Rear Steering Control ECU*1 Controls the turning angle of the rear wheels based on the signals received from the Front steering control ECU.
    Main Body ECU (Multiplex Network Body ECU) Sends the driver side door opening or closing state signal and seat belt fasten condition signal to the skid control ECU.
    Absorber Control ECU Controls the damping force based on the signals received from the skid control ECU assembly.
    Driving Support ECU Assembly*2 Makes a request for brake control to the skid control ECU assembly.
    Airbag ECU Assembly

    • Sends the collision detection signal to the skid control ECU.*2

    • Sends the driver side seat belt fasten condition signal to the main body ECU (multiplex network body ECU).
    Clearance Warning ECU Assembly*3 Sends the brake request signal to the skid control ECU.
    Central Gateway ECU (Network Gateway ECU) Relays and transmits each CAN communication data signal.
    Combination Meter Assembly Brake Warning Light / Red (Malfunction)

    • Illuminates to alert the driver that the skid control ECU assembly 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 assembly detects a malfunction in the ABS.
    Slip Indicator Light

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

    • Illuminates to alert the driver when the skid control ECU assembly detects a malfunction in the TRC or VSC.
    VSC OFF Indicator Light Illuminates to inform the driver when VSC OFF mode is selected.
    Brake Hold Indicator Light (Green Indicator) Illuminates to inform the driver that the brake hold standby condition has been established.
    Brake Hold Indicator Light (Yellow Indicator)

    • Illuminates to inform the driver that the brake hold is operating.

    • Blinks to alert the driver when the skid control ECU assembly detects a malfunction in the brake hold.
    Multi-information Display

    • Displays the warning message when the skid control ECU detects a malfunction in the system.

    • Displays the information message when TRC OFF mode is selected.
    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: Models with LDH system

    *2: Models with pre-collision system

    *3: Models with parking support brake system

  2. OPERATING CONDITION


    1. Hill-start Assist Control


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

        Control Start Conditions

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

        • The brake pedal is depressed and the vehicle is stopped.

        • The accelerator pedal is not depressed.

        • The parking brake is not applied.

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

        Control Canceling Conditions

        • The shift position is shifted to P or N.

        • The accelerator pedal is depressed.

        • The parking brake is applied.

        • 2 seconds have elapsed since the driver release the brake pedal.

    2. Brake Hold


      1. Brake Hold Standby Condition


        • To operate the brake hold, it is first necessary to establish the brake hold standby condition. The brake hold standby condition is established when the driver presses the brake hold switch after all the conditions listed below have been met. As a result, the brake hold indicator light (green indicator) illuminates in the combination meter assembly.

          Brake Hold Standby Conditions

          • The hybrid control system, electric parking brake system and electronically controlled brake system are all operating normally.

          • The driver door is closed.

          • The driver seat belt is buckled.

      2. Brake Hold Operation Condition


        • When all of the conditions listed below are met while the brake hold standby condition is established, the brake hold will operate. When the brake hold operates, the brake hold indicator light (yellow indicator) will illuminate in the combination meter assembly.

          Brake Hold Operation Conditions

          • The shift position is in any position other than P or R.

          • The brake pedal is depressed and the vehicle is stopped.

          • The accelerator pedal is not depressed.

          • The vehicle is not on a steep gradient.

          Tech Tips

          If the brake hold is inoperative because the vehicle is on a steep gradient, the system informs the driver by turning off the brake hold indicator light (yellow indicator) and outputting a warning message on the multi-information display. To support the start off of the vehicle on a steep uphill gradient, hill-start assist control will operate.

      3. Brake Hold Operation Ending Condition


        • When one of the conditions listed below has been established, the skid control ECU assembly ends the brake hold function. In addition, the skid control ECU informs the driver that the brake hold function has ended by turning off the brake hold indicator light (yellow indicator).

          Brake Hold Operation Ending Conditions

          • The accelerator pedal is depressed.

          • The shift position is shifted to P.

          • The shift position is shifted to R while depressing the brake pedal.

      4. Electric Parking Brake Operation Condition


        • If any one of the conditions listed below is established while the brake hold function is operating and the driver is not depressing the brake pedal, the electric parking brake will lock automatically.

          Electric Parking Brake Operation Conditions

          • The driver door is open

          • The driver seat belt is unbuckled.

          • 3 minutes have elapsed since the brake hold function operated.

          Tech Tips

          After the electric parking brake is locked, make sure to operate the manual function or automatic parking brake release function to release the parking brake before starting off. For details, see the Electric Parking Brake System section.

      5. Brake Hold Standby Condition Canceling Condition


        • If any one of the conditions listed below occurs while the brake hold standby condition is established, the skid control ECU assembly cancels the brake hold standby condition.

          Brake Hold Standby Condition Canceling Conditions

          • The electric parking brake has locked automatically as a result of the driver seat belt being unbuckled or the driver door being opened.

          • Any one of the following takes place while the vehicle is being driven: the driver seat belt is unbuckled or the driver door is opened.

          • The brake hold switch is pressed while the brake hold function is inoperative.

          • The brake hold switch is pressed while the brake pedal is depressed and the brake hold function is operating.

      6. Brake Hold Operation Prohibition Condition


        • If any system malfunction listed below occurs, the skid control ECU assembly prohibits the operation of the brake hold function. At this time, the skid control ECU assembly alerts the driver by flashing the brake hold indicator light (yellow indicator).

          Brake Hold Operation Prohibition Conditions

          • A hybrid control system malfunction occurs.

          • An electric parking brake system malfunction occurs.

          • An electronically controlled brake system malfunction occurs.*

          Tech Tips

          *: When the wheel cylinder pressure cannot be maintained while the brake hold function is operating, the parking brake automatically locks. After the electric parking brake is locked, make sure to operate the manual function or automatic parking brake release function to release the parking brake before starting off. For details, see the Electric Parking Brake System section.

    3. Secondary Collision Brake


      1. Secondary Collision Brake Operation Start Condition


        • When a collision detection signal is received from the airbag ECU assembly while the vehicle speed is approximately 10 km/h or more, the secondary collision brake starts operating.

          Tech Tips

          When a system malfunction is displayed on the multi-information display or the system is in test mode or maintenance mode, the secondary collision brake is prohibited from operating.

      2. Secondary Collision Brake Operation Cancellation Condition


        • If one of the following conditions is detected, operation of the secondary collision brake is canceled.

          Secondary Collision Brake Operation Cancellation Conditions

          • The vehicle speed is below approximately 10 km/h.

          • Operation continues for a certain period of time.

          • After operating, the accelerator pedal is depressed a certain amount or more.

    4. Emergency Brake Signal


      1. Operation Conditions of the emergency brake signal


        • Emergency brake signal operates when all of the following conditions have been met:

          Emergency Brake Signal Operation Conditions

          • The vehicle speed is approximately 55 km/h or more.

          • The brake pedal is depressed and the vehicle is judged to be rapidly braking based on the deceleration rate.

      2. Cancellation conditions of the emergency brake signal


        • If any one of the following conditions is met during emergency brake signal operation, emergency brake signal will be canceled.

          Emergency Brake Signal Cancellation Conditions

          • When the hazard warning lights are turned on by operating the hazard warning signal switch.

          • The brake pedal is released.

          • The parking brake is applied.

          • The deceleration rate of the vehicle is judged not to be high. The vehicle is judged not to be rapidly braking based on the deceleration rate.

  3. SYSTEM CONTROL


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

      Control Outline
      Electronically Controlled Brake System The electronically controlled brake system detects the amount that the brake pedal is depressed based on signals from the brake pedal stroke sensor. The system uses the skid control ECU assembly to adjust the pressure supplied from the hydraulic pressure source for each wheel, generating optimal braking force.
      Regenerative Braking Cooperative Control This control performs cooperative control with regenerative braking that is specific to hybrid vehicles to efficiently charge the HV battery.
      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 utilizes 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 The steering cooperative control effects cooperative control with the power steering ECU assembly, FR steering control ECU*3 and RR steering control ECU*3 in order to provide steering assist in accordance with the operating conditions of the vehicle.
      Brake Hold Function As the driver depresses the brake pedal and the vehicle comes to a stop, this function maintains the hydraulic pressure of the 4 wheels in order to keep the vehicle stopped.
      Emergency Brake Signal*1 In case of emergency braking, the emergency brake signal flashes the brake lights to alert drivers in following vehicles.
      Secondary Collision Brake*2 After the airbags operate, this system automatically operates the brakes to suppress movement after a collision.

      *1: Except models for Korea

      *2: Models with pre-collision system

      *3: Models with LDH system

  4. FAIL-SAFE


    1. If a malfunction is detected in the brake system, the fail-safe function operates. Depending on the type of malfunction, the fail-safe function informs the driver via warning indicators in the combination meter assembly and continues brake control via the use of non-malfunctioning parts. Also, when the system is not operating, the fluid pressure generated in the brake master cylinder by the depression of the brake pedal works as a back-up mechanism to ensure braking force.

  5. DIAGNOSIS


    1. A diagnosis function is provided in consideration of serviceability in order to simplify the inspection of systems. For details of the diagnosis function, refer to Repair Manual.