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 ECU, sensor and switch, and sends the brake control signals to the brake actuator.

    • Requests steering torque assist during cooperative control with EPS.
    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.
    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 Built into the brake actuator, detects the master cylinder pressure.
    Steering Sensor Detects the steering direction and angle of the steering wheel.
    Airbag ECU Assembly Yawrate Sensor

    • The airbag ECU 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 ECU assembly sends the detection signals from the yawrate sensor and acceleration sensor to the skid control ECU via CAN communication.
    Acceleration Sensor
    Power Steering ECU Assembly Receives the signal of steering torque assist request from the skid control ECU.
    Speed Sensors Detect the wheel speed of each of the 4 wheels.
    Stop Light Switch Assembly Detects when the brake pedal is depressed.
    Brake Pedal Load Sensing Switch Detects when the brake pedal is depressed.
    Brake Master Cylinder Reservoir Assembly Brake Fluid Level Warning Switch Detects the brake fluid level.
    Combination Switch Assembly VSC OFF Switch Enables the driver to select the "Normal Mode", "TRC OFF Mode", or "VSC OFF Mode".
    Brake Hold Switch Switches the brake hold function on and off.
    Vacuum Booster Pressure Sensor Detects the internal pressure of vacuum booster.
    Atmospheric Pressure Sensor* Detects the atmospheric pressure.
    ECM

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

    • Based on the signals from the skid control ECU, controls the engine output.
    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.
    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 of "VSC OFF Mode" being 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.
    Buzzer Sounds together with a message display on the multi-information display during a system malfunction.
    Master Warning Light Illuminates when the warning message is displayed in the multi-information display.
    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.
    Engine Stop and Start ECU Receives a brake hold request signal and performs brake hold control.

    *: Models for 2AR-FE engine

  2. 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 to 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.
      Cooperative Control with EPS Effects cooperative control with the power steering ECU assembly in order to provide steering assist in accordance with the operating conditions of the vehicle.
      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 When starting uphill, this control maintains the brake hydraulic pressure to all 4 wheels, in order to momentarily help prevent the vehicle from descending backward.
      Emergency Brake Signal In the case of emergency braking, the emergency brake signal flashes the hazard warning lights to alert drivers in following vehicles.
      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.

  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.