ANTI-LOCK BRAKE 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.

  2. ABS with EBD OPERATIONS


    1. Based on the signals received from each of the 4 wheel speed sensors, the skid control ECU calculates the speed of each wheel and checks the wheel slippage conditions. The ECU controls the pressure holding valve and pressure reduction valve in order to adjust the brake fluid pressure of each wheel cylinder in accordance with the slippage conditions.

  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.
    Pump Motor Drives the pumps inside the brake actuator assembly.
    Solenoid Valves

    • The hydraulic circuit has 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.
    Stop Light Switch Assembly Detects the brake pedal depressing signal.
    ECM Sends the throttle position signal, accelerator pedal position signal and engine speed signal to the skid control ECU.
    Deceleration Sensor*1 Detects the vehicle's deceleration and sends a signal to the skid control ECU.
    Combination Meter Assembly ABS Warning Light

    • Illuminates to alert the driver when the skid control ECU detects a malfunction in the ABS.

    • When the rear differential lock is in the lock state, the ABS is also prohibited and the ABS warning light turns on.*2
    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.
    Brake Master Cylinder Reservoir Assembly Brake Fluid Level Warning Switch Detects the brake fluid level.

    • *1: for 4WD and Pre-Runner

    • *2: w/ Rear Differential Lock