BRAKE CONTROL SYSTEM(for Vacuum Brake Booster)


  1. FUNCTION OF MAIN COMPONENTS

    Models without VSC
    Component Function
    Combination Meter Assembly Brake System Warning Light

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

    • Illuminates to alert the driver when the brake fluid level is low.

    • Illuminates to inform the driver of the parking brake condition.
    ABS Warning Light Illuminates to alert the driver when the skid control ECU detects a malfunction in the ABS or brake assist.
    Front and Rear Speed Sensors Detect the wheel speed of each of the 4 wheels.
    Stop Light Switch Assembly Detects the brake pedal depressing signal.
    Parking Brake Switch Assembly Detects that the parking brake lever is pulled up.
    Brake Pedal Load Sensing Switch Detects the brake pedal load.
    Transfer Shift Actuator Assembly Center Differential Lock Detection Switch Detects the transfer drive mode.
    Brake Actuator Assembly Actuator Portion Changes 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.
    Master Cylinder Pressure Sensor Detects the master cylinder pressure.
    Motor Relay Supplies power to the pump motor.
    Motor Cut Relay Cuts off power to the pump motor.
    Solenoid Relay Supplies power to the solenoid valves.
    Skid Control ECU Judges the vehicle driving conditions based on the signals from each sensor, and sends the brake control signals to the brake actuator.
    Center Airbag Sensor Assembly Yaw Rate Sensor Detects the vehicle's yaw rate.
    Deceleration Sensor Detects the vehicle's longitudinal and lateral acceleration.
    Models with VSC
    Component Function
    Combination Meter Assembly Brake System Warning Light

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

    • Illuminates to alert the driver when the brake fluid level is low.
    Parking Brake Indicator Light Illuminates to inform the driver of the parking brake condition.
    ABS Warning Light Illuminates to alert the driver when the skid control ECU detects a malfunction in the ABS or brake assist.
    Slip Indicator Light

    • Blinks to inform the driver when the TRC or VSC is operational.

    • Illuminates to alert the driver when the skid control ECU detects a malfunction in the TRC and/or VSC.
    TRC OFF Indicator Light Illuminates to inform the driver that the TRC OFF mode has been entered using the VSC OFF switch.
    VSC OFF Indicator Light Illuminates to inform the driver that the VSC OFF mode has been entered using the VSC OFF switch.
    Front and Rear Speed Sensors Detect the wheel speed of each of the 4 wheels.
    Steering Angle Sensor Detects the direction and angle of the steering wheel.
    Stop Light Switch Assembly Detects the brake pedal depressing signal.
    Parking Brake Switch Assembly Detects that the parking brake lever is pulled up.
    Brake Pedal Load Sensing Switch Detects the brake pedal load.
    VSC OFF Switch Enables the driver to select "Normal Mode", "TRC OFF Mode" or "VSC OFF Mode".
    Transfer Shift Actuator Assembly Center Differential Lock Detection Switch Detects the transfer drive mode.
    Brake Actuator Assembly Actuator Portion Changes 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.
    Master Cylinder Pressure Sensor Detects the master cylinder pressure.
    Motor Relay Supplies power to the pump motor.
    Motor Cut Relay Cuts off power to the pump motor.
    Solenoid Relay Supplies power to the solenoid valves.
    Skid Control ECU Judges the vehicle driving conditions based on the signals from each sensor, and sends the brake control signals to the brake actuator.
    ECM

    • Sends the throttle position signal, accelerator pedal position signal, engine speed signal etc., to the skid control ECU.

    • Makes a request for brake control to the skid control ECU assembly.

    • Controls the engine output based on the signals received from the skid control ECU.
    4WD Control ECU Sends the transfer drive mode.
    Center Airbag Sensor Assembly Yaw Rate Sensor Detects the vehicle's yaw rate.
    Deceleration Sensor Detects the vehicle's longitudinal and lateral acceleration.
    Driving Support ECU* Makes a request for brake control to the skid control ECU.

    *: Models with pre-crash safety system

  2. OPERATING CONDITION


    1. The brake control function varies by the drive mode as shown in the following table:

      Drive Mode Brake Control Function
      ABS EBD Brake Assist TRC VSC Hill-start Assist Control
      H4F ○ ○ ○ ○ ○ ○
      H4L ○ ○ ○ ○ ○ ○
      L4L ○ ○ ○ ○ X ○

      Tech Tips

      ○: Controls

      X: Does not control

    2. Hill-start Assist Control


      1. Hill-start assist control operates when all of the following conditions have been met:

        Control Start Conditions

        • The shift lever is in any position other than P, N or R (when forward climbing).*1

        • The shift lever is in any position other than R (when forward climbing).*2

        • The shift lever is in R (when backward climbing).

        • The vehicle is at a standstill.

        • The accelerator pedal is not depressed.

        • The parking brake is not applied.

        *1: Models with automatic transmission

        *2: Models with manual transmission

      2. If any one of the following conditions is met during hill-start assist control operation, hill-start assist control will be canceled.

        Control Cancelation Conditions

        • The shift lever is moved to P, N or R (when forward climbing).*1

        • The shift lever is moved to R (when forward climbing).*2

        • The shift lever is moved to a position other than R (when backward climbing).

        • The accelerator pedal is depressed.

        • The parking brake is applied.

        • Approximately 2 seconds elapse since the operation started.

        *1: Models with automatic transmission

        *2: Models with manual transmission

  3. SYSTEM CONTROL

    Control Outline
    Anti-lock Brake System (ABS) The ABS helps prevent the wheels from locking when the brakes are applied firmly or when braking on a slippery surface.
    Electronic Brake Force Distribution (EBD) The EBD control utilizes ABS, achieving 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 behavior.
    Brake Assist

    • The primary purpose of brake assist is to provide an auxiliary brake force to assist a driver who cannot generate a large brake force during emergency braking, thus helping ensure the vehicle's braking performance.

    • If the brake booster malfunctions and the skid control ECU judges that the brake pedal force applied by the driver is not sufficient to ensure adequate braking force, brake assist is used to enhance the braking force.
    Traction Control (TRC) The TRC helps restrain the slippage of the drive wheels if the driver depresses the accelerator pedal excessively when starting off or while accelerating on a slippery surface.
    Vehicle Stability Control (VSC) The VSC helps restrain sideways slippage of the vehicle during a strong front wheel skid or strong rear wheel skid, such as may occur while cornering.
    Hill-start Assist Control When starting uphill, this control maintains the brake hydraulic pressure on all 4 wheels in order to momentarily prevent the vehicle from descending backward.

    1. Anti-lock Brake System (ABS)


      1. The ABS prevents the wheels from locking during sudden braking or braking on a slippery surface. This provides the proper braking force when the vehicle slips, ensuring vehicle stability and excellent braking performance.

        B001BIUE01
        Text in Illustration (Illustration Provides Conceptual Image)
        *A Models with ABS *B Models without ABS
        *a Brake Operation - -

    2. Electronic Brake Force Distribution (EBD)


      1. This function controls the brake force that acts on the rear wheels in accordance with the changes in the vehicle conditions such as load factors or deceleration, in order to ensure excellent braking performance.

        B001BUKE10
        B001BMDE10

      2. During cornering braking, this function controls the brake force that acts on the left and right wheels in accordance with the vehicle conditions. This ensures vehicle stability and excellent braking performance.

        B001BPK
        Text in Illustration
        B001B9L Control Moment B001BOY Brake Force

    3. Brake Assist


      1. During brake assist, the skid control ECU calculates the speed of the brake pedal application based on the signals from the master cylinder pressure sensor and then determines the intention of the driver to make an emergency brake application. If the skid control ECU determines that the driver intends to make an emergency brake application, this function activates the brake actuator to increase the brake fluid pressure, which increases the brake force.

        B001BVZE11

    4. Traction Control (TRC)


      1. The TRC helps prevent the drive wheels from slipping if the driver depresses the accelerator pedal excessively when starting off or accelerating on a slippery surface. Simultaneously with hydraulic brake control of the drive wheels, the skid control ECU makes a request to the ECM to perform engine output control. This produces the drive force that suits the driving conditions, in order to ensure the proper start-off acceleration.

        B001BVOE07
        Text in Illustration (Driving on Road with Different Surface Friction Characteristics)
        *A Models without TRC *B Models with TRC
        *1

        ECM

        - Engine Output Control

        		 *2

        Brake Actuator Assembly

        - Hydraulic Brake Control
        *a Brake Slipping Drive Wheel - -
        B001B8G Slippery Surface - -

    5. Vehicle Stability Control (VSC)


      1. The following are 2 examples that can be considered circumstances in which the tires exceed their lateral grip limit. The VSC is designed to help control the vehicle behavior by controlling the engine output and the brakes of each wheel when the vehicle is under one of the conditions indicated below:

        B001BJPE04
        Text in Illustration
        *a

        Front Wheel Skid Tendency (Understeer)

        - When the front wheels lose grip in relation to the rear wheels

        		 *b

        Rear Wheel Skid Tendency (Oversteer)

        - When the rear wheels lose grip in relation to the front wheels

      2. To determine the condition of the vehicle, sensors detect the steering angle, vehicle speed, vehicle yaw rate and vehicle's lateral acceleration, which are then calculated by the skid control ECU.

      3. Whether or not the vehicle is experiencing a front wheel skid is determined by the difference between the target yaw rate and the vehicle's actual yaw rate. When the vehicle's actual yaw rate is smaller than the target yaw rate (which is determined based on the vehicle speed and steering angle) that should be generated when the driver operates the steering wheel, it means the vehicle is making a turn at a greater angle than the target locus of travel. Thus, the skid control ECU determines that there is a large front wheel skid tendency.

        B001BO0E05
        Text in Illustration
        *a Actual Locus of Travel (Actual Yaw Rate) *b Locus of Travel Based on Target Yaw Rate

      4. Whether or not the vehicle is experiencing a rear wheel skid is determined by the values of the vehicle's slip angle and the vehicle's slip angular velocity (time-dependent changes in the vehicle's slip angle). When the vehicle's slip angle is large, and the slip angular velocity is also large, the skid control ECU determines that the vehicle has a large rear wheel skid tendency.

        B001BR8E01
        Text in Illustration
        *a Travel Direction of Vehicle's Center of Gravity *b Movement of Vehicle
        *c Slip Angle - -

      5. When the skid control ECU determines that the vehicle exhibits a tendency to experience a front wheel skid or a rear wheel skid, it decreases the engine output and applies brakes ot the front or rear wheels to control the vehicle's yaw moment. The basic operation of the VSC is described below. However, the control method differs depending on the vehicle's characteristics and driving conditions.

      6. When the skid control ECU determines that there is a large front wheel skid tendency, it takes countermeasures in accordance with the extent of that tendency. The skid control ECU controls the engine output and applies brakes to the rear wheel on the inner circle of the turn in order to help restrain the front wheel skid tendency.

        B001BLT
        Text in Illustration (Front Wheel Skid Dampening at Right Turn)
        B001B9L Control Moment B001BOY Brake Force

      7. When the skid control ECU determines that there is a large rear wheel skid tendency, it takes countermeasures in accordance with the extent of that tendency. It applies brakes to the front and rear wheels of the outer circle of the turn, and generates an outward moment of inertia in the vehicle, in order to restrain the rear wheel skid tendency. Along with the reduction in the vehicle speed caused by the braking force, excellent vehicle stability is ensured. In some cases, the skid control ECU applies a brake to the rear wheels, as necessary.

        B001BKV
        Text in Illustration (Rear Wheel Skid Dampening at Right Turn)
        B001B9L Control Moment B001BOY Brake Force

    6. Hill-start Assist Control


      1. When the vehicle starts off on a steep or slippery hill, it could descend backward while the driver switches from the brake pedal to the accelerator pedal, making it difficult for the vehicle to start off. To prevent this from occurring, hill-start assist control temporarily (approximately 2 seconds at the maximum) applies brakes to all the wheels in order to prevent the vehicle from descending backward.

      2. Without hill-start assist control, the driver must quickly and precisely switch from the brake pedal to the accelerator pedal. With hill-start assist control, however, the driver can start off easily and operate the pedal in a relaxed manner because hill-start assist control prevents the vehicle from descending backward.

        B001BHTE07

  4. FUNCTION


    1. VSC OFF Switch


      1. The operation of the VSC and TRC functions can be stopped by the VSC OFF switch. While the vehicle is running off the shoulder of the road or running on a dirt road, engine output control is stopped to maintain the drive torque.

        B001B6LC01
        *A Models with Automatic Transmission *B Models with Manual Transmission
        *1

        Combination Meter Assembly


        • TRC OFF Indicator Light

        • VSC OFF Indicator Light

        		 *2 VSC OFF Switch

      2. The VSC OFF switch can select 3 modes (mode A, mode B and mode C).

      3. Briefly pressing the VSC OFF switch in mode A selects mode B.

      4. Pressing and holding the VSC OFF switch for 3 seconds or more with the vehicle stopped selects mode C.

      5. Briefly pressing the VSC OFF switch in mode B or mode C or turning the ignition switch off returns to mode A.

      6. When TRC is not operating, the TRC OFF indicator light illuminates.

      7. When VSC is not operating, the VSC OFF indicator light illuminates.

        B001BQ3E08
        Function of VSC OFF Switch
        Transfer Drive Mode Brake Control Function VSC OFF Switch Mode
        Mode A Mode B Mode C
        H4F TRC Operates Does Not Operate Does Not Operate
        VSC Operates Operates Does Not Operate
        H4L TRC Operates Does Not Operate Does Not Operate
        VSC Operates Does Not Operate Does Not Operate
        L4L TRC Operates - Does Not Operate
        VSC Does Not Operate - Does Not Operate

  5. CONSTRUCTION


    1. Yaw Rate Sensor and Deceleration Sensor


      1. A yaw rate sensor and deceleration sensor are built into the center airbag sensor assembly.

      2. The yaw rate sensor detects the vehicle's yaw rate.

      3. The deceleration sensor detects the vehicle's longitudinal and lateral acceleration.

        B001BXTC01
        *1

        Center Airbag Sensor Assembly


        • Yaw Rate Sensor

        • Deceleration Sensor

        		 - -

    2. Steering Angle Sensor


      1. The steering angle sensor detects the steering direction and angle, and sends this information to the skid control ECU.

        B001BG7C01
        *1 Detection Gear - -

    3. Speed Sensor


      1. Active type speed sensors, which can detect the rotational direction of the wheel, have been provided. This type of sensor contains a Hall IC, which consists of 2 Magnetic Resistance Elements (MREs).

      2. The magnet type rotor, which consists of N and S poles that are arranged in a circle, is integrated with the hub bearing inner race.

        B001BXNE04
        Text in Illustration (Front Axle)
        *1 Front Speed Sensor *2 Sensor Rotor
        B001BAPE04
        Text in Illustration (Rear Axle)
        *1 Rear Speed Sensor *2 Sensor Rotor

    4. Stop Light Switch Assembly


      1. A non-contact type stop light switch assembly with high durability is used.

      2. The movement of the magnet placed on the shaft is detected by the magnetic sensor.

      3. 2 magnetic sensors are installed and they output stop light illumination signals and cruise control system cancel signals.

        B001BKFC01
        *A Models with VSC *B Models without VSC
        *1 Stop Light Switch Assembly - -
        *a Stop Light Switch Assembly Cross Section - -

    5. Brake Actuator Assembly


      1. The brake actuator assembly consists of an actuator portion and a skid control ECU.

        B001BOBE06
        Text in Illustration
        *1 Actuator Portion *2 Skid Control ECU
        B001BC7E07
        Text in Illustration
        *1 Master Cylinder Pressure Sensor *2 Master Cylinder Cut Solenoid Valve
        *3 Pressure Holding Solenoid Valve *4 Pressure Reduction Solenoid Valve
        *5 Pump *6 Reservoir
        *a From Master Cylinder *b Front Brake LH
        *c Front Brake RH *d Rear Brake RH
        *e Rear Brake LH - -

  6. OPERATION


    1. Speed Sensor


      1. The active type speed sensor uses a sensor IC to detect magnetic field changes caused when the sensor rotor rotates, and the sensor outputs the detected information to the skid control ECU as digital pulses.

        B001B84E04

      2. To detect the rotation direction, the output waves are used to determine the relationship of the pulses that are generated by the 2 Magnetic Resistance Elements (MREs).

      3. Upon receiving this signal, the Hall IC outputs a forward or backward wave.

        B001C01E08
        *1 Forward
        *2 MRE A: Hi
        *3 MRE B: Lo
        B001B6VE08
        *1 Backward
        *2 MRE A: Hi
        *3 MRE B: Hi

      4. The frequency of the output pulses is used to detect the vehicle speed. Because the active type sensor outputs digital pulses, it can detect vehicle speeds even when the vehicle is nearly stationary.

        B001B7YE08
        *1 Vehicle Speed
        *2 Sensor Output

    2. ABS and EBD


      1. Based on the signals received from the 4 speed sensors, the skid control ECU calculates the speed of each wheel, and checks the wheel slipping conditions. In accordance with the slipping condition, the skid control ECU controls each solenoid valve in the brake actuator in order to adjust the fluid pressure of each wheel cylinder in the following 3 modes: pressure increase, pressure holding and pressure reduction modes.

        B001BAOE07
        Text in Illustration
        *1 Pressure Holding Solenoid Valve *2 Pressure Reduction Solenoid Valve
        *3 Port A *4 Port B
        *a Pressure Increase Mode *b Pressure Holding Mode
        *c Pressure Reduction Mode *d To Wheel Cylinder
        *e From Wheel Cylinder - -
        Brake Actuator Operation in ABS and EBD
        Pressure Mode Increase Mode Holding Mode Reduction Mode
        Pressure Holding Solenoid Valve [Port (A)] Off (Open) On (Closed) On (Closed)
        Pressure Reduction Solenoid Valve [Port (B)] Off (Closed) Off (Closed) On (Open)
        Wheel Cylinder Pressure Increases Holds Reduces

    3. Brake Assist


      1. In the event of emergency braking, the skid control ECU determines the driver's intention based on the speed of the pressure increase in the master cylinder determined by the master cylinder pressure sensor signal. If the skid control ECU judges the need for additional brake assist, pressure is generated by the pump in the brake actuator and directed to the wheel cylinder to apply a large amount of fluid pressure.

        B001BS8E08
        Brake Actuator Operation in Brake Assist
        Item Brake Assist Not Activated Brake Assist Activated
        Pump Off On
        Master Cylinder Cut Solenoid Valve (1) Port (A) Off (Open) On*
        (2) Port (B) Off (Open) On*
        Pressure Holding Solenoid Valve (3) Port (C) Off (Open) ←
        (4) Port (D) Off (Open) ←
        (5) Port (E) Off (Open) ←
        (6) Port (F) Off (Open) ←
        Pressure Reduction Solenoid Valve (7) Port (G) Off (Closed) ←
        (8) Port (H) Off (Closed) ←
        (9) Port (I) Off (Closed) ←
        (10) Port (J) Off (Closed) ←

        Tech Tips

        *: The solenoid valve controls the hydraulic pressure between "open" and "closed" in accordance with the operating condition by adjusting continually.

    4. TRC


      1. The fluid pressure generated by the pump is regulated by the master cylinder cut solenoid valve to the required pressure. Thus, the wheel cylinders of the drive wheels are controlled in the following 3 modes: pressure increase, pressure holding and pressure reduction modes to control the slippage of the drive wheels. The pressure holding solenoid valve and the pressure reduction solenoid valve are turned on or off in accordance with the ABS and EBD operation patterns.

        B001BS8E08
        Brake Actuator Operation in TRC
        Item TRC Operation
        Not Activated Pressure Increase Mode Pressure Holding Mode Pressure Reduction Mode
        Pump Off On ← ←
        Master Cylinder Cut Solenoid Valve (1) Port (A) Off (Open) On* ← ←
        (2) Port (B) Off (Open) On* ← ←
        Front Brake Pressure Holding Solenoid Valve (3) Port (C) Off (Open) ← On(Closed) ←
        (4) Port (D) Off (Open) ← On(Closed) ←
        Pressure Reduction Solenoid Valve (7) Port (G) Off (Closed) ← ← On (Open)
        (8) Port (H) Off (Closed) ← ← On (Open)
        Wheel Cylinder Pressure Left - Increases Holds Reduces
        Right - Increases Holds Reduces
        Rear Brake Pressure Holding Solenoid Valve (5) Port (E) Off (Open) ← On(Closed) ←
        (6) Port (F) Off (Open) ← On(Closed) ←
        Pressure Reduction Solenoid Valve (9) Port (I) Off (Closed) ← ← On (Open)
        (10) Port (J) Off (Closed) ← ← On (Open)
        Wheel Cylinder Pressure Right - Increases Holds Reduces
        Left - Increases Holds Reduces

        Tech Tips

        *: The solenoid valve controls the hydraulic pressure between "open" and "closed" in accordance with the operating condition by adjusting continually.

    5. VSC


      1. The VSC, by way of solenoid valves, controls the fluid pressure generated by the pump and applies it to the brake wheel cylinder of each wheel in the following 3 modes: pressure increase, pressure holding and pressure reduction modes. As a result, the tendency to front wheel skid or rear wheel skid is controlled.

      2. In front wheel skid restraining control, a brake of the front wheel on the outer circle of the turn and the rear wheels is applied. Also, depending on whether the brake is on or off and also depending on the condition of the vehicle, there are circumstances in which a brake might not be applied to the wheels even if the wheel is targeted for braking. The following diagram shows the hydraulic circuit in the pressure increase mode, as it controls the front wheel skid condition while the vehicle is making a right turn. In other operating modes, the pressure holding valve and the pressure reduction valve are turned on or off in accordance with the ABS and EBD operation patterns.

        B001BU4E04
        Brake Actuator Operation in VSC (Front Wheel Skid Restraining)
        Item VSC Operation
        Not Activated Pressure Increase Mode Pressure Holding Mode Pressure Reduction Mode
        Pump Off On ← ←
        Master Cylinder Cut Solenoid Valve (1) Port (A) Off (Open) On* ← ←
        (2) Port (B) Off (Open) On* ← ←
        Front Brake Pressure Holding Solenoid Valve (3) Port (C) Off (Open) ← On (Closed) ←
        (4) Port (D) Off (Open) On (Closed) ← ←
        Pressure Reduction Solenoid Valve (7) Port (G) Off (Closed) ← ← On (Open)
        (8) Port (H) Off (Closed) ← ← ←
        Wheel Cylinder Pressure Left - Increases Holds Reduces
        Right - - - -
        Rear Brake Pressure Holding Solenoid Valve (5) Port (E) Off (Open) ← On (Closed) ←
        (6) Port (F) Off (Open) ← On (Closed) ←
        Pressure Reduction Solenoid Valve (9) Port (I) Off (Closed) ← ← On (Open)
        (10) Port (J) Off (Closed) ← ← On (Open)
        Wheel Cylinder Pressure Right - Increases Holds Reduces
        Left - Increases Holds Reduces

        Tech Tips

        *: The solenoid valve controls the hydraulic pressure between "open" and "closed" in accordance with the operating condition by adjusting continually.

      3. During rear wheel skid restraining control, brakes of the front wheel on the outer circle of the turn are applied. Also, depending on whether the brake is on or off and also depending on the condition of the vehicle, there are circumstances in which a brake might not be applied to the wheels even if the wheel is targeted for braking. The following diagram shows the hydraulic circuit in the pressure increase mode, as it controls the rear wheel skid condition while the vehicle is making a right turn. In other operating modes, the pressure holding valve and the pressure reduction valve are turned on or off in accordance with the ABS and EBD operation patterns.

        B001C04E05
        Brake Actuator Operation in VSC (Rear Wheel Skid Restraining)
        Item VSC Operation
        Not Activated Pressure Increase Mode Pressure Holding Mode Pressure Reduction Mode
        Pump Off On ← ←
        Master Cylinder Cut Solenoid Valve (1) Port (A) Off (Open) On* ← ←
        (2) Port (B) Off (Open) On* ← ←
        Front Brake Pressure Holding Solenoid Valve (3) Port (C) Off (Open) ← On (Closed) ←
        (4) Port (D) Off (Open) On (Closed) ← ←
        Pressure Reduction Solenoid Valve (7) Port (G) Off (Closed) ← ← On (Open)
        (8) Port (H) Off (Closed) ← ← ←
        Wheel Cylinder Pressure Left - Increases Holds Reduces
        Right - - - -
        Rear Brake Pressure Holding Solenoid Valve (5) Port (E) Off (Open) On (Closed) ← ←
        (6) Port (F) Off (Open) On (Closed) ← ←
        Pressure Reduction Solenoid Valve (9) Port (I) Off (Closed) ← ← ←
        (10) Port (J) Off (Closed) ← ← ←
        Wheel Cylinder Pressure Right - - - -
        Left - - - -

        Tech Tips

        *: The solenoid valve controls the hydraulic pressure between "open" and "closed" in accordance with the operating condition by adjusting continually.

    6. Hill-start Assist Control


      1. Hill-start assist control operation is performed by closing the master cylinder cut solenoid valves after the driver operates the brake pedal and leaving a certain amount of the hydraulic pressure created by the pump in the wheel cylinder. The diagram below shows the hydraulic circuit in the pressure holding mode.

        B001BZ3E01
        Brake Actuator Operation in Hill-start Assist Control
        Item Hill-start Assist Control Operation
        Not Activated Pressure Holding Mode Pressure Reduction Mode
        Master Cylinder Cut Solenoid Valve (1) Port (A) Off (Open) On (Closed) Off (Open)
        (2) Port (B) Off (Open) On (Closed) Off (Open)
        Front Brake Pressure Holding Solenoid Valve (3) Port (C) Off (Open) ← ←
        (4) Port (D) Off (Open) ← ←
        Pressure Reduction Solenoid Valve (7) Port (G) Off (Closed) ← On (Open)
        (8) Port (H) Off (Closed) ← On (Open)
        Wheel Cylinder Pressure Left - Holds Reduces
        Right - Holds Reduces
        Rear Brake Pressure Holding Solenoid Valve (5) Port (E) Off (Open) ← ←
        (6) Port (F) Off (Open) ← ←
        Pressure Reduction Solenoid Valve (9) Port (I) Off (Closed) ← On (Open)
        (10) Port (J) Off (Closed) ← On (Open)
        Wheel Cylinder Pressure Right - Holds Reduces
        Left - Holds Reduces

  7. FAIL-SAFE


    1. If a failure occurs in the skid control ECU, sensors or brake actuator, the system continues performing brake control by excluding the failed area and using only the areas that are operating normally.

  8. DIAGNOSIS


    1. If the skid control ECU detects a malfunction in the brake control system, the warning or indicator lights illuminate. At the same time, a Diagnostic Trouble Code (DTC) is stored in the memory of the skid control ECU.

    2. This system has a sensor signal check (test mode) function.

    3. For details of DTC and check function, refer to the Repair Manual.