VEHICLE STABILITY CONTROL SYSTEM SYSTEM DESCRIPTION

  1. FUNCTION DESCRIPTION

    1. ABS (Anti-lock Brake System)

      1. The ABS helps prevent the wheels from locking when the brakes are applied firmly or when braking on a slippery surface.

    2. EBD (Electronic Brake force Distribution)

      1. The EBD control utilizes ABS, and performs proper brake force distribution between the front and rear wheels in accordance with driving conditions. When braking while cornering, it also controls the brake forces of the right and left wheels, helping to maintain vehicle stability.

    3. BA (Brake Assist)

      1. The primary purpose of the brake assist system is to provide auxiliary brake force to assist the driver if the driver cannot generate a large enough brake force during emergency braking, thus helping to maximize the brake performance of the vehicle.

    4. TRC/TRAC (Traction Control)

      1. The TRC/TRAC system helps prevent the drive wheels from slipping when the driver depresses the accelerator pedal excessively when starting off or accelerating on a slippery surface.

    5. VSC (Vehicle Stability Control)

      1. The VSC system helps prevent the vehicle from slipping sideways as a result of strong front or rear wheel skid during cornering.

    6. Hill-start Assist Control (w/ Stop Light Control Relay)

      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.

    7. Downhill Assist Control (w/ Downhill Assist Control)

      1. When the downhill assist control switch is pressed with the shift lever in L or R and the accelerator and brake pedals not depressed, downhill assist control is activated. When activated, 4-wheel hydraulic pressure control occurs in order to maintain a constant low vehicle speed without causing the wheels to become locked. Thus, the vehicle can descend a steep hill in a stable manner.

    8. AUTO LSD (for 2WD)

      1. The AUTO LSD achieves the equivalent functions of an LSD (Limited Slip Differential) through the use of a traction control system. When the driver momentarily presses the VSC OFF switch (traction control switch), this system achieves the LSD effect by regulating the hydraulic pressure that acts on the drive wheels and controlling the engine output in accordance with the amount of pedal effort applied on the accelerator. The AUTO LSD operates with the VSC OFF switch (traction control switch) on and the accelerator pedal depressed.

  2. ABS with EBD, BA, TRC/TRAC and VSC OPERATIONS

    1. The skid control ECU (brake actuator assembly) calculates vehicle stability tendency based on the signals from the speed sensor, yaw rate and acceleration sensor (airbag sensor assembly), and steering angle sensor (spiral with sensor cable sub-assembly). In addition, it evaluates the results of the calculations to determine whether any control actions (control of the engine output torque by electronic throttle control and of the wheel brake pressure by the brake actuator assembly) should be implemented.

    2. The slip indicator blinks to inform the driver that the VSC system is operating. The slip indicator also blinks when traction control is operating.

  3. INITIAL CHECK

    1. When the vehicle speed first reaches approximately 6 km/h (4 mph) or more after the ignition switch is turned to ON, each solenoid valve and motor in the brake actuator is sequentially activated to perform an electrical check. During the initial check, the operating sound of the solenoid valves and motors can be heard from the engine compartment, but this is not a malfunction.

  4. 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

    Motor Relay

    Supplies power to the pump motor.

    Solenoid Relay

    Supplies power to the solenoid valves.

    Speed Sensor

    Detects the wheel speed of each of the 4 wheels.

    VSC OFF Switch (Traction Control Switch)

    Enables the driver to select the Normal mode, TRC/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 and engine speed signal to the skid control ECU.

    • Controls the engine output based on the signals received from the skid control ECU.

    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 acceleration.

    • The airbag sensor assembly sends the detection signals from the yaw rate sensor and acceleration sensor to the skid control ECU via CAN communication.

    Spiral with Sensor Cable Sub-assembly

    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.

    TRC/TRAC OFF Indicator Light*1

    Illuminates to inform the driver when TRC/TRAC off mode is selected.

    VSC OFF Indicator Light

    Illuminates to inform the driver when VSC off mode is selected.

    Slip Indicator Light

    • Blinks to inform the driver when the TRC/TRAC or VSC system is performing control.

    • Illuminates to alert the driver when the skid control ECU detects a malfunction in the TRC/TRAC and/or VSC system.

    Downhill Assist Control Indicator Light*2

    Illuminates to inform the driver when downhill assist control operation is possible.

    AUTO LSD Indicator Light*3

    Illuminates to inform the driver when AUTO LSD operation is possible.

    Multi-information Display*4

    Displays to inform the driver that TRC OFF mode is entered using the VSC OFF switch (traction control switch).

    Meter Buzzer

    Emits a warning sound to inform the driver during brake control operation (operating hill-start assist control).

    Brake Master Cylinder Reservoir Sub-assembly

    Brake Fluid Level Warning Switch

    Detects the brake fluid level.

    • *1: for Segment Display Type

    • *2: w/ Downhill Assist Control

    • *3: for 2WD

    • *4: for Dot Display Type