BRAKE CONTROL SYSTEM(w/ Vacuum Brake Booster)


  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 Load Sensing Switch Detects the brake pedal load.
    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.
    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.
    Brake Actuator Assembly Solenoid Relay (Built into Skid Control ECU) Supplies power to the solenoid valves.
    Motor Relay (Built into Skid Control ECU) Supplies power to the pump motor.
    Motor Cut Relay (Built into Skid Control ECU) Cuts the power to the pump motor when the motor relay malfunctions.
    Solenoid Valves Change the fluid path based on the signals from the skid control ECU during the operation of the brake control system functions in order to control the fluid pressure applied to the wheel cylinders.
    Pump Motor Drives the pumps inside the brake actuator.
    Master Cylinder Pressure Sensor Detects the master cylinder pressure.
    Skid Control ECU

    • Judges the vehicle driving condition based on the signals from each ECU, sensor and switch, and sends the brake control signals to the brake actuator.

    • Performs comprehensive control in accordance with Vehicle Dynamics Integrated Management (VDIM) according to communication with each ECU.
    ECM

    • Controls the drive 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.
    Power Steering ECU with Motor Assembly Power Steering ECU Controls the steering assist torque based on the signals received from the skid control ECU.
    Front Steering Control ECU*1

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

    • 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.
    Absorber Control ECU*2 Controls the damping force based on the signals received from the skid control ECU.
    Driving Support ECU Assembly*3 Sends the brake request signal to the skid control ECU.
    Engine Stop and Start ECU*4 Sends the brake request signal to the skid control ECU.
    Clearance Warning ECU Assembly*5 Sends the brake request signal to the skid 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.
    Airbag ECU Assembly

    • Sends the collision detection signal to the skid control ECU.*3

    • Sends the driver side seat belt fasten condition signal to the main body ECU (multiplex network body ECU).
    Central Gateway ECU (Network Gateway ECU) Relays and transmits each CAN communication data signal.
    Active Stabilizer Control ECU Assembly*6 Controls the front active stabilizer control actuator assembly according to stabilizer bar twisting angle signals from the front steering control ECU and skid control ECU.
    Rear Active Stabilizer Control ECU Assembly*6 Controls the rear active stabilizer control actuator assembly according to stabilizer bar twisting angle signals from the front steering control ECU and skid control ECU.
    Combination Meter Assembly Brake Warning Light / Red (Malfunction)

    • Illuminates to alert the driver when the skid control ECU detects a malfunction in the EBD or brake system.

    • Illuminates to inform the driver when the brake fluid is low.
    Brake Warning Light / Yellow (Minor Malfunction) Illuminates to alert the driver when the electric parking brake ECU assembly detected a malfunction in the electric parking brake system.
    ABS Warning Light Illuminates to alert the driver when the skid control ECU detects a malfunction in the ABS.
    Slip Indicator Light

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

    • Illuminates to alert the driver when the skid control ECU 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 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 or blinks 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 AVS

    *3: Models with pre-collision system

    *4: Models with stop and start system

    *5: Models with parking support brake system

    *6: Models with active stabilizer suspension 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 engine control system, electric parking brake system and 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 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 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 prohibits the operation of the brake hold function. At this time, the skid control ECU alerts the driver by flashing the brake hold indicator light (yellow indicator).

          Brake Hold Operation Prohibition Conditions

          • A engine control system malfunction occurs.

          • An electric parking brake system malfunction occurs.

          • A brake system and brake control system malfunction occurs.*

          • An ECT 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
      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, front steering control ECU*3 and rear 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 failure occurs in the skid control ECU, sensors or brake actuator assembly, the system continues performing brake control by excluding the failed area and using only the areas that are operating normally.

  5. DIAGNOSIS


    1. If the skid control ECU detects a malfunction in the brake control system, the warning lights or indicator light illuminate. At the same time, a Diagnostic Trouble Code (DTC) is stored in the memory of the skid control ECU.

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

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