BRAKE CONTROL SYSTEM


  1. FUNCTION OF MAIN COMPONENTS

    Models without VSC
    Component Function
    Brake Actuator Assembly Solenoid Relay (Built into Skid Control ECU) Supplies power to the solenoid valves.
    Motor Relay (Built into Skid Control ECU) Supplies power to the pump motor.
    Solenoid Valves Change the fluid path based on signals from the skid control ECU during the operation of brake control system functions in order to control the fluid pressure applied to the wheel cylinders.
    Pump Motor Drives the pumps inside the brake actuator.
    Skid Control ECU Determines the vehicle driving condition based on the signals from each ECU, sensor and switch, and sends brake control signals to the brake actuator.
    Speed Sensors Detect the wheel speed of each of the 4 wheels.
    A.D.D. Actuator (Differential Motor Actuator Assembly)*1 A.D.D. Position Switch Detects the A.D.D. actuator operating condition.
    Transfer Shift Actuator Assembly*2 4WD Detection Switch Detects the 4WD position condition.
    L4 Detection Switch Detects the L4 position condition.
    Rear Differential Lock Position Switch (Transfer Indicator Switch)*3 Detects the rear differential lock condition.
    Deceleration Sensor*4 Detects the vehicle's longitudinal and lateral acceleration.
    Stop Light Switch Assembly Detects the brake pedal depression signal.
    4 Wheel Drive Control ECU*5 Outputs signals such as the L4 position condition signal, 4WD position condition signal and rear differential lock condition signal*3 to the skid control ECU via CAN communication.
    Combination Meter Assembly ABS Warning Light Illuminates to alert the driver when the skid control ECU detects a malfunction in the ABS.
    Brake System Warning Light Illuminates to alert the driver when the skid control ECU detects a malfunction in the EBD.

    • *1: Models with A.D.D. actuator

    • *2: 4WD models

    • *3: Models with rear differential lock system

    • *4: 2WD PreRunner and 4WD models

    • *5: 2WD PreRunner models with rear differential lock system and 4WD models

    Models with VSC
    Component Function
    Brake Actuator Assembly Solenoid Relay (Built into Skid Control ECU) Supplies power to the solenoid valves.
    Motor Relay (Built into Skid Control ECU) Supplies power to the pump motor.
    Motor Cut Relay (Built into Skid Control ECU) Cuts the power to the pump motor when the motor relay malfunctions.
    Solenoid Valves Change the fluid path based on signals from the skid control ECU during the operation of brake control system functions in order to control the fluid pressure applied to the wheel cylinders.
    Pump Motor Drives the pumps inside the brake actuator.
    Master Cylinder Pressure Sensor Detects the master cylinder pressure.
    Skid Control ECU Determines the vehicle driving condition based on the signals from each ECU, sensor and switch, and sends brake control signals to the brake actuator.
    Speed Sensors Detect the wheel speed of each of the 4 wheels.
    A.D.D. Actuator (Differential Motor Actuator Assembly)*1 A.D.D. Position Switch Detects the A.D.D. actuator operating condition.
    Transfer Shift Actuator Assembly*2 4WD Detection Switch Detects the 4WD position condition.
    L4 Detection Switch Detects the L4 position condition.
    Rear Differential Lock Position Switch (Transfer Indicator Switch)*3 Detects the rear differential lock condition.
    Airbag Sensor Assembly Yawrate Sensor Detects the vehicle's yaw rate.
    Deceleration Sensor Detects the vehicle's longitudinal and lateral acceleration.
    Steering Angle Sensor Detects the steering direction and angle of the steering wheel.
    Stop Light Switch Assembly Detects the brake pedal depression signal.
    Parking Brake Switch Assembly Detects the parking brake lever status.
    Neutral Position Switch*4 Detects the neutral position condition.
    VSC OFF Switch Enables the driver to select "Normal Mode", "TRC OFF Mode" or "VSC OFF Mode".
    Downhill Assist Control Switch*5 Allows the driver to turn downhill assist control on and off.
    4 Wheel Drive Control ECU*6 Outputs signals such as the L4 position condition signal, 4WD position condition signal and rear differential lock condition signal*3 to the skid control ECU via CAN communication.
    Combination Meter Assembly ABS Warning Light Illuminates to alert the driver when the skid control ECU detects a malfunction in the ABS.
    Brake System Warning Light Illuminates to alert the driver when the skid control ECU detects a malfunction in the EBD.
    Parking Brake Indicator Light Illuminates to inform the driver when the parking brake is applied.
    Slip Indicator Light

    • Blinks to inform the driver when TRC, A-TRC*2, VSC or downhill assist control*5 is operational.

    • Illuminates to alert the driver when the skid control ECU detects a malfunction in the brake control function.
    TRC OFF Indicator Light*7

    • Illuminates to inform the driver when TRC OFF mode is selected.

    • Illuminates together with the VSC OFF indicator light to inform the driver when VSC OFF mode is selected.
    VSC OFF Indicator Light Illuminates to inform the driver when VSC OFF mode is selected.
    Downhill Assist Control Indicator Light*5 Illuminates to inform the driver when downhill assist control operation is possible.
    Multi-information Display*8

    • Displays a message to inform the driver when in TRC OFF Mode.

    • Displays a warning message to alert the driver when the skid control ECU detects a malfunction in the brake control function.
    ECM

    • Outputs signals such as the shift position signal*9, back-up light switch signal*10, accelerator pedal position signal, throttle position signal*11, clutch switch signal*4 and engine speed signal to the skid control ECU via CAN communication.

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

    • *1: Models with A.D.D. actuator

    • *2: 4WD models

    • *3: Models with rear differential lock system

    • *4: Models with manual transmission and downhill assist control

    • *5: Models with downhill assist control

    • *6: 2WD PreRunner models with rear differential lock system and 4WD models

    • *7: Models without multi-information display

    • *8: Models with multi-information display

    • *9: Models with automatic transmission

    • *10: Models with manual transmission

    • *11: Models with gasoline engine

  2. OPERATING CONDITION


    1. 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

    2. Downhill Assist Control


      1. Downhill assist control operates when all of the following conditions are met with the downhill assist control switch turned on:

        Control Operation Conditions

        • The transfer drive mode is in H4 or L4.

        • The rear differential is unlocked.*1

        • The shift lever is in any position other than P.*2

        • The accelerator pedal and brake pedal are not depressed.

        • The vehicle speed is 30 km/h (19 mph) or less while moving downhill.

        • *1: Models with rear differential lock system

        • *2: Models with automatic transmission

        Tech Tips

        When the accelerator pedal and brake pedal are operated while downhill assist control is operating, control is performed in a manner that does not interfere with acceleration and deceleration operations by the driver.

      2. Downhill assist control does not operate under the conditions described below even if the downhill assist control switch is turned on. In this case, the downhill assist control indicator light blinks to alert the driver.

        Control Cancelation Conditions

        • The transfer drive mode is changed to any position other than H4 or L4.

        • The rear differential is locked.*1

        • The shift lever is moved to P.*2

        • The vehicle speed is greater than about 30 km/h (19 mph).

        • A malfunction occurs in the downhill assist control system.

        • The temperature of the brake actuator rises, causing the downhill assist control operation to stop.

        • *1: Models with rear differential lock system

        • *2: Models with automatic transmission

        Tech Tips

        The downhill assist control indicator light flashes to warn the driver when any of the following conditions is met, but downhill assist control is still performed.


        • The downhill assist control switch is turned off while downhill assist control is operating. Afterward, brake hydraulic pressure gradually decreases and downhill assist control stops.

        • The shift lever is moved to N (models with automatic transmission).

        • The clutch is disengaged while driving with the shift lever in N (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) EBD control utilizes the 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.
    Traction Control (TRC) TRC helps restrain the slippage of the drive wheels if the driver depresses the accelerator pedal excessively when starting off or accelerating on a slippery surface.
    Active Traction Control (A-TRC) A-TRC controls the brake hydraulic pressure that is applied to the slipping wheel, and distributes the drive force that would have been lost through the slippage to the remaining wheels in order to achieve an LSD effect.
    Vehicle Stability Control (VSC) VSC helps restrain sideways slippage of the vehicle during a strong front wheel skid or a strong rear wheel skid, either of which may occur while cornering.
    Trailer Sway Control If the tongue load is not properly adjusted while towing a trailer, trailer sway may be caused due to crosswinds, bumpy roads, steering operation, etc. Trailer sway control detects sway and regulates the brake of each wheel and the engine output in order to suppress trailer sway.
    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.
    Downhill Assist Control When the downhill assist control switch is pressed while the transfer drive mode is in H4 or L4, and without accelerator or brake pedal operation, downhill assist control activates to perform 4-wheel hydraulic pressure control, 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.

  4. FAIL-SAFE


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

  5. DIAGNOSIS


    1. If the skid control ECU detects a malfunction in the brake control system, the warning lights or indicator light 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 DTC and check function details, refer to the Repair Manual.