BRAKE CONTROL SYSTEM


  1. FUNCTION OF MAIN COMPONENTS

    Component Function
    Brake Actuator Assembly Skid Control ECU Judges the vehicle driving condition based on the signals from each sensor, and sends brake control signals to the brake actuator.
    Solenoid Valve (10) Changes the fluid path based on the signals from the skid control ECU during the operation of the ABS with EBD, Brake Assist, TRC and VSC, in order to control the fluid pressure that is applied to the wheel cylinders.
    Motor Drives the pumps inside the brake actuator.
    Solenoid Relay Supplies power to the solenoid valves.
    Motor Relay Supplies power to the motor.
    Motor Failsafe Relay Cuts the power to the motor when the motor relay malfunctions.
    Master Cylinder Pressure Sensor Assembled in the brake actuator, detects the master cylinder pressure.
    Steering Angle Sensor Detects the steering direction and angle of the steering wheel.
    Yaw Rate and Acceleration Sensor (Airbag Sensor Assembly) Detects the yaw rate and the longitudinal and lateral acceleration and deceleration of the vehicle body.
    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 when the parking brake lever is pulled up.*1 Detects the parking brake pedal status.*2
    Brake Fluid Level Warning Switch Detects the brake fluid level.
    VSC OFF Switch Enables the driver to select the "Normal Mode", "TRC-OFF Mode", or "VSC-OFF Mode".

    Main Body ECU

    (Multiplex Network Body ECU)

    		 Transmits the parking brake switch assembly signal to the skid control ECU.
    ECM

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

    • Based on the signals receives from the skid control ECU, controls the engine output.
    Power Steering ECU Assembly Operates cooperatively with the skid control ECU to control the steering assist torque.
    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.
    Parking Brake Warning Light Illuminates to inform the driver when the parking brake is operated.
    Slip Indicator Light

    • Illuminates to alert the driver if the TRC or VSC system malfunctions.

    • Blinks to inform the driver when the TRC or VSC operates.
    TRC OFF Indicator Light Illuminates to inform the driver of "TRC-OFF mode" or "VSC-OFF mode" being selected.
    VSC OFF Indicator Light Illuminates to inform the driver of "VSC-OFF mode" being selected.

    Tech Tips

    *1: Models with center lever type parking brake.

    *2: Models with foot-operated type parking brake.

  2. SYSTEM CONTROL


    1. Control List

      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, realizing 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 the Brake Assist is to provide an auxiliary brake force to assist the driver who cannot generate a large brake force during emergency braking, thus helping draw the vehicle's brake performance.
      Traction Control (TRC) 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.
      Vehicle Stability Control (VSC) The VSC helps prevent the vehicle from slipping sideway as a result of strong front wheel skid or strong rear wheel skid during cornering.
      Engine Output Control during TRC or VSC Operation Transmits an engine output control signal from the skid control ECU to the ECM to limit the engine output while the TRC or VSC is being activated.
      VSC+ (Cooperative Control with EPS) Effects cooperative control with the power steering ECU assembly in order to provide steering assist in accordance with the operating conditions of the vehicle.

    2. 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, thus ensuring vehicle stability and excellent braking performance.

        A005FUKE09
        Text in Illustration
        *1 with ABS *2 without ABS
        *3 Brake Operation - -

    3. Electronic Brake Force Distribution (EBD)


      1. The distribution of the brake force, which was performed mechanically in the past, is now performed under electrical control of the skid control ECU, which controls the braking force in accordance with the vehicle's driving conditions.

      2. If the brakes are applied while the vehicle is moving straight forward, the transfer of the load reduces the weight that is applied to the rear wheels. The skid control ECU determines this condition by way of the signals from the speed sensor, and the brake actuator regulates the distribution of the brake force of the rear wheels to optimally control. For example, the amount of the brake force that is applied to the rear wheels during braking varies depending on whether the vehicle is carrying load or not. The amount of the brake force that is applied to the rear wheels also varies in accordance with the extent of the deceleration. Thus, the distribution of the brake force to the rear is optimally controlled in order to effectively utilize the braking force of the rear wheels under these conditions.

        A005FRYE18

      3. When the brakes are applied while the vehicle is cornering, the load that is applied to the inner wheel decreases as the load to the outer wheel increases. The skid control ECU determines this condition by way of the signals from the speed sensor, and the brake actuator regulates the brake force in order to optimally control the distribution of the brake force to the inner wheel and outer wheel.

        A005FUDE02
        Text in Illustration
        *1 Control Moment *2 Brake Force

    4. Brake Assist


      1. The Brake Assist in combination with the ABS helps ensure the vehicle's brake performance.

      2. The Brake Assist interprets a quick push of the brake pedal as emergency braking and supplements the brake force applied if the driver has not depressed hard enough the brake pedal. In emergencies, drivers, especially inexperienced ones, often panic and do not apply sufficient pressure on the brake pedal.

      3. A key feature of Brake Assist is that the timing and the degree of braking assistance are designed to help ensure that the driver dose not discern anything unusual about the braking operation. When the driver intentionally eases up on the brake pedal, the system reduces the amount of assistance it provides.

      4. Based on the signals from the master cylinder pressure sensor, the skid control ECU calculates the speed and the amount of the brake pedal application and then determines the intention of the driver to make an emergency braking. If the skid control ECU determines that the driver intends emergency braking, the system activates the brake actuator to increase the brake fluid pressure, which increases the braking force.

        A005G42E03

    5. Traction Control (TRC)


      1. If the driver depresses the accelerator pedal aggressively when initially acceleration or when accelerating on a slippery surface, the drive wheels could slip due to the excessive amount of torque that is generated. By applying hydraulic brake control to the drive wheels and regulating the throttle to control the engine output, the TRC helps minimize the slippage of the drive wheels, thus generating the drive force that is appropriate for the road surface conditions.

      2. For example, a comparison may be made between 2 vehicles, one with the TRC and the other without. If the driver of each vehicle operates the accelerator pedal in a rough manner while driving over a surface with different surface friction characteristics, the drive wheel on the slippery surface could slip as illustrated. As a result, the vehicle could become unstable. However, when the vehicle is equipped with the TRC, the skid control ECU instantly determines the state of the vehicle and operates the brake actuator in order to apply the brakes to the slipping drive wheel. Furthermore, the ECM receives the signals from the skid control ECU and regulates the throttle in order to control the engine output. Thus, the system can constantly maintain a stable vehicle posture.

        A005G2QE04
        Text in Illustration
        *1 Driving condition on road with different surface friction characteristics *2 without TRC
        *3 with TRC *4 Slippery Surface
        *5 Brake the slipping drive wheel *6

        • Brake Actuator Assembly


          • Skid Control ECU
        *7 ECM - -

    6. Vehicle Stability Control (VSC)


      1. The followings are two examples that can be considered as circumstances in which the tires exceed their lateral grip limit. The VSC is designed to help control the vehicle behavior by controlling the motive force and the brakes at each wheel when the vehicle is under one of the conditions indicated below.


        • When the front wheels lose grip in relation to the rear wheels (front wheel skid tendency).

        • When the rear wheels lose grip in relation to the front wheels (rear wheel skid tendency).

        A005G6IE05
        Text in Illustration
        *1 Front Wheel Skid Tendency *2 Rear Wheel Skid Tendency

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

      3. Whether or not the vehicle is in the state of 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 yaw rate (a target yaw rate that is determined by the vehicle speed and steering angle) that should be rightfully generated when the driver operates the steering wheel, it means the vehicle is making a turn at a greater angle than the locus of travel. Thus, the skid control ECU determines that there is a large tendency to front wheel skid.

        A005FY4E04
        Text in Illustration
        *1 Actual Locus of Travel (Actual Yaw Rate) *2 Locus of Travel (Based on the Target Yaw Rate)

      4. Whether the vehicle is in the state of the rear wheel skid or not 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 and the slip angular velocity are large, the skid control ECU determines that the vehicle has a large rear wheel skid tendency.

        A005G9XE04
        Text in Illustration
        *1 Movement of Vehicle *2 Direction of Travel of the Vehicle's Center of Gravity
        *3 Slip Angle - -

      5. When the skid control ECU determines that the vehicle has a tendency to front wheel skid or rear wheel skid, it decreases the engine output and applies the brake of a front or rear wheel 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 the brakes of the front wheels and rear wheel of the inner circle of the turn in order to help restrain the front wheel skid tendency.

        A005FSLE05
        Text in Illustration
        *1 Control Moment *2 Making a Right Turn
        *3 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 the brakes of 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.

        A005FYQE02
        Text in Illustration
        *1 Control Moment *2 Making a Right Turn
        *3 Brake Force - -

    7. Engine Output Control during TRC or VSC Operation


      1. During the TRC or VSC operation, the skid control ECU outputs the engine output control signal to the ECM. Upon receiving this signal, the ECM inhibits the engine output.

        A005FONE05

    8. VSC+ (Cooperative Control with EPS)


      1. If the driver suddenly applies the brakes on a road surface with a considerable difference in friction coefficient between the right and left wheels, the difference in the brake force between the right and left wheels will cause the vehicle posture to become unstable and create a yaw moment. In this state, the skid control ECU controls the ABS and VSC to stabilize the vehicle posture. At the same time, it effects cooperative control with the EPS to provide steering torque assist, which facilitates the driver's steering maneuvers to stabilize the vehicle posture.

        A005G0KE04
        *1 Assisting Direction
        *2 Yaw Moment during Brake Controlling
        *3 Slippery Surface
        *4 Brake Force

      2. If the driver suddenly starts off or accelerates on a road surface with a considerable difference in friction coefficient between the right and left wheels, the slippage of a drive wheel will cause the vehicle posture to become unstable and negatively affect its acceleration performance. In this state, the skid control ECU causes the TRC to control the hydraulic brake of the slipping drive wheel, and requests the ECM to effect engine output control. At the same time, it effects cooperative control with the EPS to provide steering torque assist, which facilitates the driver's steering maneuvers to stabilize the vehicle posture.

        A005GC4E03
        *1 Assisting Direction
        *2 Yaw Moment during Accelerating
        *3 Slippery Surface
        *4 Drive Force

      3. When the skid control ECU determines a front wheel skid tendency, it controls the VSC to dampen the front wheel skid. At the same time, it effects the cooperative control with the EPS to provide steering torque assist, which controls the driver's steering maneuvers to stabilize the vehicle posture. Steering torque assists are provided to inform the driver of the front wheel skid, and to prevent the driver's excessive turning of the steering wheel. In the assist for preventing excessive turning, it increases the resistance to counter the driver's steering effort, if the driver turns the steering wheel excessively.

        A005G1VE04

      4. When the skid control ECU determines a rear wheel skid tendency, it controls the VSC to dampen the rear wheel skid. At the same time, it effects the cooperative control with the EPS to provide steering torque assist, which facilitates the driver's steering maneuvers in the direction to correct the rear wheel skid.

        A005G94E03
        *1 Control Moment
        *2 Assisting Direction
        *3 Rear Wheel Skid Tendency
        *4 Brake Force

  3. FUNCTION


    1. VSC OFF Switch (Models with VSC)


      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 the dirt road, the engine output control is stopped to maintain drive torque.

      2. The VSC OFF switch can select the 3 modes (Normal Mode, TRC-OFF Mode, VSC-OFF Mode). When the VSC OFF switch is pressed briefly, TRC-OFF Mode is entered and the TRC function will be disabled. When the VSC OFF switch is pressed and held for 3 seconds or more, VSC-OFF Mode is entered and the TRC and VSC functions will be disabled.

      3. After the power source is turned off in the TRC-OFF Mode or VSC-OFF Mode, turning the power source on again selects the Normal Mode. The system also enters Normal Mode automatically when the vehicle speed increases.

        A005G4PE02

      4. The operations of the brake control functions in each mode are as follows:

        Item Brake Control Function TRC OFF Indicator Light VSC OFF Indicator Light
        TRC VSC
        Normal Mode ○ ○ Does not Illuminate Does not Illuminate
        TRC-OFF Mode - ○ Illuminates Does not Illuminate
        VSC-OFF Mode - -* Illuminates Illuminates

        • ○: Controllable

        • -: Not Controllable

        Tech Tips

        *: The control is effected during braking or while the yaw rate is large.

  4. CONSTRUCTION


    1. Brake Actuator Assembly


      1. The brake actuator consists of the actuator portion and skid control ECU.

      2. The actuator portion regulates the hydraulic brake pressure to each wheel cylinder.

        A005G3XE05
        Text in Illustration
        *1 from Master Cylinder *2 Actuator Portion
        *3 to Front Brake RH *4 to Rear Brake LH
        *5 to Rear Brake RH *6 to Front Brake LH
        *7 Skid Control ECU - -

      3. The brake actuator is constructed with the following hydraulic circuit:

        A005GB7E02
        Text in Illustration
        *1 Hydraulic Circuit *2 from Master Cylinder
        *3 Brake Actuator Assembly *4 Master Cylinder Pressure Sensor
        *5 Master Cylinder Cut Solenoid Valve *6 Pressure Holding Solenoid Valve
        *7 Pump *8 Pressure Reduction Solenoid Valve
        *9 Reservoir *10 Front Left Wheel Cylinder
        *11 Rear Right Wheel Cylinder *12 Rear Left Wheel Cylinder
        *13 Front Right Wheel Cylinder - -

    2. Speed Sensor


      1. An active type speed sensor is used. This sensor contains a Hall IC.

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

      3. An active type speed sensor uses a Hall 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.

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

        A005FPQE11

    3. Yaw Rate and Acceleration Sensor (Airbag Sensor Assembly)


      1. The yaw rate and acceleration sensor is built into the airbag sensor assembly.

      2. The yaw rate sensor detects acceleration in the horizontal forward-backward and left-right directions using the signals from 2 acceleration sensors, and transmits signals to the skid control ECU.

        A005G1HE02
        Text in Illustration
        *1 Yaw Rate and Acceleration Sensor (Airbag Sensor Assembly) *2 Front

        Note

        After replacing the yaw rate sensor, or the skid control ECU, initialization of the yaw rate sensor is required. For the actual procedure, refer to the Repair Manual.

    4. Steering Angle Sensor


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

      2. The steering angle sensor contains 2 sets of magnetic reluctance elements that detect the rotational movement of a magnet that is built into the detection gear. Thus, the sensor detects the changes that occur in the magnetic reluctance elements along with the rotational movement of the detection gear, in order to detect the rotational movement of the steering wheel.

        A005FTXE02
        Text in Illustration
        *1 Steering Angle Sensor *2 Detection Gear

        Note

        Do not remove the steering angle sensor from the spiral cable. If there is a malfunction in the steering angle sensor, replace the spiral cable with steering angle sensor.

  5. OPERATION


    1. ABS with EBD


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

        A005FNUE05
        Not Activated Normal Braking - -
        Activated Increase Mode Holding Mode Reduction Mode
        Pressure Holding Valve (Port A) OFF (Open) ON (Close) ←
        Pressure Reduction Valve (Port B) OFF (Close) ← ON (Open)
        Wheel Cylinder Pressure Increase Hold Reduce

    2. Brake Assist


      1. In the event of emergency braking, the skid control ECU detects 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 greater fluid pressure than the master cylinder.

        A005G0QE04
        A005FR1E04
        Item Port Not Activated Activated
        Master Cylinder Cut Solenoid Valve (1) (A) OFF (Open) ON*
        (2) (B) OFF (Open) ON*
        Pressure Holding Solenoid Valve (3) (C) OFF (Open) ←
        (4) (D) OFF (Open) ←
        (5) (E) OFF (Open) ←
        (6) (F) OFF (Open) ←
        Pressure Reduction Solenoid Valve (7) (G) OFF (Closed) ←
        (8) (H) OFF (Closed) ←
        (9) (I) OFF (Closed) ←
        (10) (J) OFF (Closed) ←
        Pump OFF ON

        Tech Tips

        *: The solenoid valve controls the hydraulic pressure between "open" and "close" according to the operating condition by adjusting continually.

    3. 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 reduction, pressure holding, and pressure increase modes to control the slippage of the drive wheels. The diagram below shows the hydraulic circuit in the pressure increase mode when the TRC is activated. The pressure holding solenoid valve and the pressure reduction solenoid valve are turned on/off according to the ABS with EBD operation pattern.

        A005FW6E04

      2. By way of example, the brake hydraulic circuit under the pressure increase mode of TRC is shown below.

        A005G2SE04
        Item Port Not Activated Activated
        Increase Mode Holding Mode Reduction Mode
        Master Cylinder Cut Solenoid Valve (1) (A) OFF (Open) ON* ← ←
        (2) (B) OFF (Open) ON* ← ←
        Front Brake Pressure Holding Solenoid Valve (3) (C) OFF (Open) ← ← ON (Closed)
        (6) (F) OFF (Open) ← ← ON (Closed)
        Pressure Reduction Solenoid Valve (7) (G) OFF (Closed) ← ← ON (Open)
        (10) (J) OFF (Closed) ← ← ON (Open)
        Brake Wheel Cylinder Pressure Right - - Increase Hold Reduce
        Left - - Increase Hold Reduce
        Rear Brake Pressure Holding Solenoid Valve (4) (D) OFF (Open) ON (Closed) ← ←
        (5) (E) OFF (Open) ON (Closed) ← ←
        Pressure Reduction Solenoid Valve (8) (H) OFF (Closed) ← ← ←
        (9) (I) OFF (Closed) ← ← ←
        Brake Wheel Cylinder Pressure Right - - - - -
        Left - - - - -
        Pump OFF ON ← ←

        Tech Tips

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

    4. VSC


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

        A005FTHE04

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

        A005FSYE04
        Item Port Not Activated Activated
        Increase Mode Holding Mode Reduction Mode
        Master Cylinder Cut Solenoid Valve (1) (A) OFF (Open) ON* ← ←
        (2) (B) OFF (Open) ON* ← ←
        Front Brake Pressure Holding Solenoid Valve (3) (C) OFF (Open) ← ON (Closed) ←
        (6) (F) OFF (Open) ← ON (Closed) ←
        Pressure Reduction Solenoid Valve (7) (G) OFF (Closed) ← ← ON (Open)
        (10) (J) OFF (Closed) ← ← ON (Open)
        Brake Wheel Cylinder Pressure Right - - Increase Hold Reduce
        Left - - Increase Hold Reduce
        Rear Brake Pressure Holding Solenoid Valve (4) (D) OFF (Open) ← ON (Closed) ←
        (5) (E) OFF (Open) ON (Closed) ← ←
        Pressure Reduction Solenoid Valve (8) (H) OFF (Closed) ← ← ON (Open)
        (9) (I) OFF (Closed) ← ← ←
        Brake Wheel Cylinder Pressure Right - - Increase Hold Reduce
        Left - - - - -
        Pump OFF ON ← ←

        Tech Tips

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

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

        A005FS6E04
        Item Port Not Activated Activated
        Increase Mode Holding Mode Reduction Mode
        Master Cylinder Cut Solenoid Valve (1) (A) OFF (Open) ON* ← ←
        (2) (B) OFF (Open) ON* ← ←
        Front Brake Pressure Holding Solenoid Valve (3) (C) OFF (Open) ← ON (Closed) ←
        (6) (F) OFF (Open) ON (Closed) ← ←
        Pressure Reduction Solenoid Valve (7) (G) OFF (Closed) ← ← ON (Open)
        (10) (J) OFF (Closed) ← ← ←
        Brake Wheel Cylinder Pressure Right - - - - -
        Left - - Increase Hold Reduce
        Rear Brake Pressure Holding Solenoid Valve (4) (D) OFF (Open) ON (Closed) ← ←
        (5) (E) OFF (Open) ← ON (Closed) ←
        Pressure Reduction Solenoid Valve (8) (H) OFF (Closed) ← ← ←
        (9) (I) OFF (Closed) ← ← ON (Open)
        Brake Wheel Cylinder Pressure Right - - - - -
        Left - - Increase Hold Reduce
        Pump OFF ON ← ←

        Tech Tips

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

    5. VSC+ (Cooperative Control with EPS)


      1. The operation of the solenoid valves under the cooperative control with EPS is the same as the brake control functions (ABS, TRC, VSC) operation.

  6. FAIL-SAFE


    1. In the event of a malfunction in the ABS, skid control ECU prohibits the brake control system.

    2. In the event of a malfunction in the EBD, the brake system is operated as long as possible even if the ABS is prohibited. If the EBD control becomes impossible, the brake warning light illuminates to inform the driver of that. In this case, the brake system is operated in the same condition as the brake system without the brake control system.

    3. In the event of a malfunction in the TRC and/or VSC, skid control ECU prohibits the TRC and VSC operation.

    4. If a communication malfunction occurs between the skid control ECU and the steering angle sensor, yaw rate sensor, or ECM, the skid control ECU stops the TRC and VSC.

    5. When the ECM detects the DTC (Diagnostic Trouble Code), it will disable the TRC and VSC.

  7. DIAGNOSIS


    1. If the skid control ECU detects a malfunction in the brake control system (ABS with EBD, brake assist, TRC, VSC and VSC+), then the ABS warning light, brake warning light, or slip indicator light illuminate either individually or as a group according to the function in which the malfunction has been detected, to alert the driver of the malfunction.

    2. At the same time, the DTCs (Diagnostic Trouble Codes) are stored in memory.

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

    4. For details of the DTCs that are stored in skid control ECU memory and the DTCs that are output through the sensor signal check functions, see the Repair Manual.