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.
    Stop Light Switch Assembly Detects the brake pedal depression signal.
    Stop Light Control ECU Assembly

    • Automatically flashes the stop lights during emergency braking.

    • Illuminates the stop lights when the dynamic radar cruise control system, pre-collision system and brake hold function activate.
    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.
    Integration Control and Panel Assembly VSC OFF Switch Enables the driver to select normal mode, TRC OFF mode or VSC OFF mode.
    Brake Hold Switch Switches the brake hold function on and off.
    Brake Actuator Assembly 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.
    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.
    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.

    • Requests steering torque assist during cooperative control with EPS.

    • Requests torque distribution between the front and rear wheels during cooperative control with AWD.*1
    ECM

    • Outputs signals such as the shift position signal, Sport mode signal, throttle position signal and engine speed signal to the skid control ECU.

    • Controls the engine output based on the signals from the skid control ECU.
    Parking Brake ECU Assembly

    • Sends the electric parking brake condition to the skid control ECU.

    • Controls the parking brake actuator assembly based on the signals received from the skid control ECU.
    Power Steering ECU Controls the steering assist torque based on the signals received from the skid control ECU.
    Absorber Control ECU*2 Controls the damping force based on the signals received from the skid control ECU.
    4WD ECU Assembly*1 Operates in cooperation with the skid control ECU to control the torque distribution between the front and rear wheels.
    Driving Support ECU*3 Makes a request for brake control to the 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 alert the driver when the brake fluid level is low.
    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 or VSC.
    VSC OFF Indicator Light Illuminates to inform the driver when VSC OFF mode is selected.
    Brake Hold Indicator Light (Yellow Indicator)

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

    • Blinks to alert the driver when the skid control ECU detects a malfunction in the brake hold function.
    Brake Hold Indicator Light (Green Indicator) Illuminates to inform the driver that the brake hold standby condition has been established.
    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 Sounds together with a message display on the multi-information display during a system malfunction.

    • *1: AWD models

    • *2: Models with AVS

    • *3: Models with pre-collision 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.

    2. Brake Hold


      1. The standby condition is necessary for brake hold operation. When the brake hold switch is pressed while all of the following conditions are met with the engine switch on (IG), the standby condition is met. When the standby condition is met, the brake hold indicator light (green indicator) illuminates.

        Conditions to Meet Standby Condition

        • Engine control system, ECT system, electric parking brake system and brake system are all operating normally.

        • Driver door is closed.

        • Driver seat belt is buckled.

      2. When the standby condition and all of the following conditions are met, the brake hold function operates. While brake hold is operating, the brake hold indicator light (yellow indicator) illuminates.

        Brake Hold Operation Conditions

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

        • The driver depresses the brake pedal and the vehicle is at a standstill.

        • The accelerator pedal is not depressed.

        • The vehicle is not on a steep slope.

        Tech Tips

        When brake hold cannot operate due to a steep slope, the brake hold indicator light (yellow indicator) stays off and a message is displayed on the multi-information display. Also, wheel cylinder hydraulic pressure is maintained for approximately 2 seconds after releasing the brake pedal to support starting off on uphill slopes.

      3. When any of the following conditions is met, brake hold ends while the brake hold indicator light (yellow indicator) turns off.

        Brake Hold Operation Ending Conditions

        • The driver depresses the accelerator pedal.

        • The driver moves the shift lever to P.

        • The driver depresses the brake pedal and moves the shift lever to R.

      4. When any of the following conditions is met with the brake pedal released during brake hold operation, the electric parking brake automatically operates. When starting off the vehicle, depress the accelerator pedal with the driver door closed and the seat belt fastened, or manually release the parking brake.

        Electric Parking Brake Operation Conditions

        • Driver door is open.

        • Driver seat belt is unbuckled.

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

      5. When any of the following conditions is met while the standby condition is met, the standby condition is canceled.

        Conditions to Cancel Standby Condition

        • 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.

        • Driver presses the brake hold switch while the brake hold function is inoperative.

        • Driver presses the brake hold switch while depressing the brake pedal and the brake hold function is operating.

      6. When a malfunction occurs in any of the following systems, brake hold operation is prohibited. At this time, the brake hold indicator light (yellow indicator) flashes to inform the driver that the brake hold function cannot operate.

        Brake Hold Operation Prohibiting Conditions

        • Brake system and brake control system malfunctions.

        • Engine control system malfunction.

        • ECT system malfunction.

        • Electric parking brake system malfunction.

      7. When the hydraulic pressure cannot be maintained during brake hold operation due to brake system and brake control system malfunctions, the parking brake automatically locks. When starting off the vehicle, depress the accelerator pedal with the driver door closed and the seat belt fastened, or manually release the parking brake.

  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 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.
      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 engine output in order to suppress trailer sway.
      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.
      Brake Hold 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.

  4. FAIL-SAFE


    1. If a failure occurs in the skid control ECU, sensors or brake actuator assembly, the system continues effecting 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.