Vehicle Stability Control System (For Sedan) System Description

Brake. Yaris. Ncp93, 131
Brake Control Dynamic Control Systems. Yaris. Ncp93, 131

  1. FUNCTION DESCRIPTION

  1. ABS with EBD, BA, TRAC and VSC OPERATION

  1. INITIAL CHECK

  1. FUNCTION OF COMPONENTS

Vehicle Stability Control System (For Sedan) -- System Description



FUNCTION DESCRIPTION

  1. ABS (Anti-lock Brake System)
    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)
    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)
    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. TRAC (Traction Control)
    The TRAC system helps prevent the drive wheels from slipping when the driver depresses the accelerator pedal excessively when starting off or when accelerating on a slippery surface.

  5. VSC (Vehicle Stability Control)
    The VSC system helps prevent the vehicle from slipping sideways as a result of strong front or rear wheel skid during cornering.


ABS with EBD, BA, TRAC and VSC OPERATION

  1. The skid control ECU calculates vehicle stability tendency based on the signals from the speed sensor, yaw rate and acceleration sensor, and steering angle sensor. 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 and the skid control buzzer sounds to inform the driver that the VSC system is operating. The SLIP indicator also blinks when traction control is operating.


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.


FUNCTION OF COMPONENTS

Component
Function
Speed sensor
Detects the wheel speed and sends the signal to the skid control ECU.
Yaw rate and acceleration sensor
  1. Acceleration sensor measures the capacity of the condenser that changes the distance between the electrodes depending on G force, which occurs when the vehicle is accelerated, and converts the measured value into electrical signals.
  2. Yaw rate sensor detects the vehicle's angular velocity (yaw rate) in the vertical direction based on the amount and direction of the piezoelectric ceramics deflection.
  3. Sends signals to the skid control ECU via CAN communication.
Steering angle sensor
  1. Installed in the combination switch.
  2. Detects the steering amount and direction and sends the signals to the skid control ECU via CAN communication.
  3. Has a magnetic resistance element which detects the rotation of the magnet housed in the detection gear in order to detect the changes in magnetic resistance and the steering amount and direction.
Stop light switch
Detects the brake operating conditions and inputs the results to the skid control ECU.
Main body ECU
Detects the parking brake operating conditions and inputs the result to the skid control ECU via CAN communication.
Master cylinder pressure sensor
  1. Detects the fluid pressure in the master cylinder.
  2. Housed in the brake actuator assembly.
Skid control ECU
  1. Housed in the brake actuator assembly.
  2. Processes the signals sent from each sensor to control the ABS, EBD, BA, TRAC, and VSC.
  3. Sends and receives the control signals to or from the ECM, yaw rate and acceleration sensor, and steering angle sensor, etc. via CAN communication.
Brake actuator assembly
  1. Consists of the master cylinder cut solenoid valve, retention solenoid valve, pressure reduction solenoid valve, pump motor, and reservoir, and adjusts the brake fluid pressure applied to each wheel cylinder.
  2. Houses the skid control ECU.
Motor relay
  1. Supplies power to the pump motor.
  2. Housed in the skid control ECU.
Motor fail safe relay
  1. Cuts off power to the motor when the pump motor circuit malfunctions.
  2. Housed in the skid control ECU.
Solenoid relay
  1. Supplies power to each solenoid.
  2. Housed in the skid control ECU.
ABS warning light
  1. Comes on to inform the driver that a malfunction in the ABS and/or BA has occurred.
  2. Blinks to output DTC.
Brake warning light
  1. Comes on to inform the driver that the parking brake is ON when the system is normal, or that the brake fluid has decreased.
  2. Comes on to inform the driver that a malfunction in the EBD has occurred.
VSC OFF indicator light
Comes on to inform the driver when the VSC OFF mode is entered using VSC OFF switch.
TRAC OFF indicator light
Comes on to inform the driver when the TRAC off mode is entered using the VSC OFF switch.
SLIP indicator light
  1. Comes on to inform the driver that a malfunction in the VSC and/or TRAC system has occurred.
  2. Blinks to inform the driver that TRAC and/or VSC are operating.
  3. Blinks to output DTC.
Skid control buzzer
  1. Housed in the combination meter assembly.
  2. Intermittently sounds to inform the driver that the VSC is operating.
ECM
Controls the engine output when TRAC and/or VSC are operating with the skid control ECU via CAN communication.
VSC OFF switch
Pressing this switch turns off traction control and pressing and holding this switch turns off traction and VSC controls.