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Home >> Toyota >> 2019 >> Corolla XLE >> Repair and Diagnosis (Single Page) >> Brakes >> Traction Control >> Vehicle Stability Control System - Diagnostics - Introduction (1 Of 2) (Model Code: ZRE172) >> Vehicle Stability Control System >> System Description [08/2015 - 08/2016] >> System Description [08/2015 - 08/2016]
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System Description [08/2015 - 08/2016]

  1. FUNCTION DESCRIPTION 
    1. Anti-lock Brake System (ABS)
      1. The ABS helps prevent the wheels from locking when the brakes are applied firmly or when braking on a slippery surface.
    2. Electronic Brake Force Distribution (EBD)
      1. EBD control utilizes the 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 forces of the right and left wheels, helping maintain vehicle stability.
    3. Brake Assist (BA)
      1. 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 ensure the vehicle's braking performance.
    4. Traction Control (TRAC)
      1. The TRAC system 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.
    5. Vehicle Stability Control (VSC)
      1. The VSC system helps restrain sideways slippage of the vehicle during a strong understeer tendency or strong oversteer tendency while cornering.
    6. 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.
  2. FUNCTION OF COMPONENTS 
    Component Function
    Brake Actuator Assembly Skid Control ECU Judges the vehicle driving condition based on the signals from each sensor, and sends the brake control signals to the brake actuator assembly.
    Master Cylinder Pressure Sensor Assembled in the brake actuator assembly, detects the master cylinder pressure.
    Pump Motor Drives the pumps inside the brake actuator assembly.
    Solenoid Valves
    • The hydraulic circuit has 2 master cylinder cut solenoid valves, 4 pressure holding solenoid valves and 4 pressure reduction 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.
    Skid Control ECU ABS Motor Relay Supplies power to the pump motor.
    ABS Solenoid Relay Supplies power to the solenoid valves.
    Speed Sensor Detects the wheel speed of each of the 4 wheels.
    VSC OFF Switch Enables the driver to select the Normal mode, TRAC off Mode, or VSC off mode.
    Stop Light Switch Assembly Detects the brake pedal depressing signal.
    Main Body ECU (Multiplex Network Body ECU) Transmits the parking brake switch signal to the skid control ECU.
    Parking Brake Switch Assembly Detects when the parking brake lever is pulled up.
    ECM
    • Sends the throttle position signal, accelerator pedal position signal engine speed signal to the skid control ECU.
    • Based on the signals receives from the skid control ECU, controls the engine output.
    Airbag Sensor Assembly Yaw Rate and Acceleration Sensor
    • The airbag sensor assembly incorporates the yaw rate sensor and acceleration sensor.
    • The yaw rate sensor detects the vehicle's yaw rate.
    • The acceleration sensor detects the vehicle's longitudinal and lateral deceleration.
    • The airbag sensor assembly sends the detection signals from the yaw rate sensor and acceleration sensor to the skid control ECU via CAN communication.
    Steering Angle Sensor Detects the steering direction and angle of the steering wheel.
    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.
    TRAC OFF Indicator Light Lights up to inform the driver of TRAC off mode or VSC off mode being selected.
    VSC OFF Indicator Light Lights up to inform the driver of VSC off mode being selected.
    Slip Indicator Light
    • Blinks to inform the driver when the TRAC or VSC operates.
    • Illuminates to alert the driver if the TRAC or VSC system malfunctions.
    Brake Master Cylinder Reservoir Sub-assembly Brake Fluid Level Warning Switch Detects the brake fluid level.
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