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Home >> Lexus >> 2012 >> IS 250C Automatic Trans >> Repair and Diagnosis >> Brakes >> Traction Control >> Vehicle Stability Control System (Diagnostics - Introduction) >> Vehicle Stability Control System >> System Description >> System Description
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System Description

  1. FUNCTION DESCRIPTION 
    1. Vehicle Dynamics Integrated Management (VDIM)
      1. VDIM integrally controls engine output and braking in coordination with steering control to ensure vehicle running, cornering and stopping performance for active safety.
    2. Steering Cooperation Control
      1. Performs cooperative control with the power steering ECU in order to provide steering torque assist in accordance with present vehicle dynamics.
    3. Anti-lock Brake System (ABS)
      1. ABS helps prevent the wheels from locking when the brakes are applied firmly or when braking on a slippery surface.
    4. Electronic Brake force Distribution (EBD)
      1. EBD control utilizes ABS, realizing proper brake force distribution between the front and rear wheels in accordance with the driving conditions. In addition, when braking while cornering, it also controls the brake forces applied to the right and left wheels, helping to stabilize vehicle behavior.
    5. 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.
    6. Traction Control (TR(A)C)
      1. 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.
    7. Vehicle Stability Control (VSC)
      1. Helps restrain sideways slippage of the vehicle during a strong understeer tendency or strong oversteer tendency while cornering
    8. Hill-start Assist Control
      1. When the vehicle starts off on a steep or a slippery hill, Hill-start Assist Control performs 4-wheel hydraulic pressure control to prevent the vehicle from moving backward.
  2. FUNCTION OF COMPONENTS 
    Component Function
    Brake actuator assembly
    • Solenoid valve
    • Master cylinder cut solenoid valve
    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 each wheel cylinder.
    Master cylinder pressure sensor Built into the brake actuator, detects the master cylinder pressure.
    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.
    Motor relay Supplies power to the pump motor.
    Solenoid relay Supplies power to the solenoid valves.
    Combination meter Brake warning light
    • Illuminates together with the ABS warning light to alert the driver when the skid control ECU detects a malfunction in the EBD control.
    • Illuminates to alert the driver when the skid control ECU detects a malfunction in the brake booster.
    • Illuminates to alert the driver when the brake fluid level is low.
    • Illuminates to inform the driver when the parking brake is applied.
    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 TR(A)C or VSC is operating.
    • Illuminates to alert the driver when the skid control ECU detects a malfunction in the TR(A)C or VSC systems.
    VSC OFF indicator light Illuminates to inform the driver when VSC OFF mode is selected.
    Multi-information display
    • Displays a warning message to alert the driver when TR(A)C OFF mode is selected.
    Meter buzzer Emits a warning sound to inform the driver during Hill-start Assist Control operation.
    Stop light control (BRK-LP) relay Illuminates the stop lights while Hill-start Assist Control is operating.
    Steering angle sensor Detects the direction and angle of the steering wheel.
    Yaw rate and acceleration sensor
    • Detects the vehicle's longitudinal and lateral acceleration and deceleration.
    • Detects the vehicle's yaw rate.
    Speed sensor Detects the wheel speed of each wheel.
    Stop light switch Detects brake pedal operation.
    Brake pedal load sensing switch Detects the brake pedal depressing force.
    Parking brake switch Detects the parking brake pedal status.
    VSC OFF switch Enables the driver to select Normal mode, TR(A)C OFF mode, or VSC OFF mode.
    ECM
    • Sends the throttle position signal, accelerator pedal position signal, engine speed signal etc., to the skid control ECU.
    • Based on the signals received from the skid control ECU, controls the engine output.