BRAKE CONTROL SYSTEM


  1. FUNCTION OF MAIN COMPONENTS

    Component Function
    Brake Actuator Assembly Skid Control ECU Judges the vehicle driving condition based on the signals from each sensor and switch, and sends the brake control signals to the brake actuator.
    Solenoid Valves

    • The hydraulic circuit has 2 master cylinder cut solenoid valves, 2 reservoir cut solenoid valves, 4 pressure holding solenoid valves and 4 pressure reduction solenoid valves.*1

    • The hydraulic circuit has 4 pressure holding solenoid valves and 4 pressure reduction solenoid valves.*2

    • 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.
    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.
    Master Cylinder Pressure Sensor*1 Bilt into the brake actuator, detects the master cylinder pressure.
    Spiral Cable with Sensor Sub-assembly*1 Steering Sensor Detects the steering direction and angle of the steering wheel.
    Airbag Sensor Assembly*1 Yawrate Sensor

    • The airbag sensor assembly incorporates the yawrate sensor and acceleration sensor.

    • The yawrate sensor detects the vehicle yaw rate.

    • The acceleration sensor detects the vehicle's longitudinal and lateral deceleration.

    • The airbag sensor assembly sends the detection signals from the yawrate sensor and acceleration sensor to the skid control ECU via CAN communication.
    Acceleration Sensor
    Speed Sensors Detect the wheel speed of each of the 4 wheels.
    Stop Light Switch Assembly Detects when the brake pedal is depressed.
    Parking Brake Switch Assembly Detects when the parking brake lever is pulled up.
    Brake Master Cylinder Sub-assembly Brake Fluid Level Warning Switch Detects the brake fluid level.
    VSC OFF Switch*1 Enables the driver to select the "Normal Mode", "TRC OFF Mode", or "VSC OFF Mode".
    Main Body ECU (Multiplex Network Body ECU) Transmits the parking brake switch signal to the skid control ECU.
    ECM*1

    • Sends the throttle position signal, accelerator pedal position signal engine speed signal to the skid control ECU.

    • Based on the signals from the skid control ECU, controls the engine output.
    Throttle Body with Motor Assembly*4 Throttle Position Sensor Detects the throttle valve opening angle and outputs it to the ECM.
    Throttle Control Motor Adjusts the throttle valve opening angle in accordance with signals from the ECM.
    Throttle Body Assembly*5 Throttle Position Sensor Detects the throttle valve opening angle and outputs it to the ECM.
    Throttle Control Motor Adjusts the throttle valve opening angle in accordance with signals from the ECM.
    Fuel Injection Control*3 Receives signals from the ECM to control the injectors.
    Combination Meter Assembly ABS Warning Light Illuminates to alert the driver when the skid control ECU detects a malfunction in the ABS.
    Brake Warning Light

    • 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.

    • Illuminates to inform the driver when the parking brake is operated.
    Slip Indicator Light*1

    • Illuminates to alert the driver if the TRC or VSC system malfunctions.

    • Blinks to inform the driver when the TRC or VSC operates.
    TRC OFF Indicator Light*1 Illuminates to inform the driver of "TRC OFF mode" or "VSC OFF mode" being selected.
    VSC OFF Indicator Light*1 Illuminates to inform the driver of "VSC OFF mode" being selected.
    Buzzer Sounds to alert the driver when the vehicle is being driven with the parking brake still engaged.
    Hazard Warning Signal Switch Assembly*1 Transmits a hazard warning light on/off request signal to the skid control ECU.
    Engine Stop and Start ECU*6 Outputs a hill-start assist operation request signal to the skid control ECU if equired.
    Pre-crash Safety City Sensor*7 Makes judgments on whether a collision is possible based on the information received from the camera and radar sensor. It then outputs a pre-crash brake request signal if required.

    *1: Models with brake control (ABS with EBD, brake assist, TRC, VSC and hill-start assist control)

    *2: Models with brake control (ABS with EBD)

    *3: Models with 1WW engine

    *4: Models with 1NR-FE or 8NR-FTS engine

    *5: Models with 1ZR-FAE, 1ZR-FE or 2ZR-FE engine

    *6: Models with stop and start system

    *7: Models with pre-crash safety system

  2. SYSTEM CONTROL


    1. Table of System Control


      1. The brake control system has the following system/functions:

        Control Outline
        Anti-lock Brake System (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) EBD control utilizes ABS, realizing proper brake force distribution between the front and rear wheels in accordance with the driving conditions. In addition, during braking while cornering, it also controls the brake force of the right and left wheels, helping maintain vehicle stability.
        Brake Assist* The primary purpose of brake assist is to provide supplementary brake force to assist a driver who cannot generate a large brake force during emergency braking, thus helping utilize the vehicle's braking performance.
        Traction Control (TRC)* Helps restrain the slippage of the drive wheels if the driver depresses the accelerator pedal excessively when starting off or accelerating on a slippery surface.
        Vehicle Stability Control (VSC)* Helps restrain sideways slippage of the vehicle during a strong understeer tendency or strong oversteer tendency while cornering.
        Engine Output Control during TRC or VSC Operation* Transmits an engine output control signal from the skid control ECU to the ECM to limit the engine output while the TRC or VSC is being activated.
        Hill-start Assist Control*1 When starting uphill, this control maintains the brake hydraulic pressure to the 4 wheels, in order to momentarily prevent the vehicle from descending backward.
        Emergency Brake Signal*1 In the case of emergency braking, the emergency brake signal flashes the hazard warning lights to alert drivers in following vehicles.
        Pre-crash Brake*1*2 When the pre-crash safety city sensor 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 pre-crash safety city sensor.

        *1: Models with brake control (ABS with EBD, brake assist, TRC, VSC and hill-start assist control)

        *2: Models with pre-crash safety system

  3. FAIL-SAFE


    1. If a malfunction occurs in the skid control ECU, sensors, or brake actuator assembly, the system continues performing brake control by excluding the malfunctioning area and using only the areas that are operating normally.

  4. 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.