ACTIVE TORQUE CONTROL 4WD SYSTEM DETAILS


  1. FUNCTION OF MAIN COMPONENTS

    Component Function
    Combination Meter Assembly Multi-information Display Displays a warning message to inform or warn the driver of the system condition in accordance with signals from the 4WD ECU assembly.
    Master Warning Light Illuminates to warn the driver if a malfunction occurs in the AWD system.
    AWD Lock Indicator Light Illuminates to inform the driver that AWD lock mode engaged.
    Speed Sensor (4) Detects the wheel speed of each wheel.
    Crankshaft Position Sensor Detects the engine speed and outputs it to the ECM.
    Throttle Position Sensor Detects the throttle valve position and outputs it to the ECM.
    Park/Neutral Position Switch Assembly Detects the shift position of the transaxle and outputs it to the ECM.
    Stop Lamp Switch Assembly Detects when the brake pedal is depressed.
    Parking Brake Switch Detects when the parking brake is applied.
    Yawrate Sensor Detects the vehicle's longitudinal acceleration and deceleration.
    Transfer Drive force input into the differential is redirected 90 degrees and output to the propeller shaft by the transfer.
    Rear Differential

    Electromagnetic Control Coupling

    - Electromagnetic Solenoid

    		 Distributes drive torque in accordance with the amperage applied by the 4WD ECU assembly.
    4WD ECU Assembly

    • Controls the amperage applied to the electromagnetic control coupling solenoid based on signals provided by the sensors in order to optimally distribute drive torque in accordance with driving conditions.

    • Turns AWD mode off when a parking brake ON signal is received from the main body ECU (multiplex network body ECU).

    • Turns AWD mode off when a shift position signal (P or N) is received from the ECM.
    ECM Outputs signals such as the shift position signal, throttle position signal, and crankshaft position signal to the 4WD ECU assembly.
    Skid Control ECU Outputs signals such as the vehicle speed signal and deceleration signal to the 4WD ECU assembly.
    Main Body ECU (Multiplex Network Body ECU) Outputs signals such as the parking brake signal to the 4WD ECU assembly.

  2. CONSTRUCTION


    1. Transfer


      1. The compact and lightweight MF1A transfer is used.

      2. Drive force input into the differential is redirected 90 degrees and output to the propeller shaft by the transfer.

      3. The offset between the transfer ring gear and the transfer driven pinion gear is increased, the distance between the driven pinion bearings is reduced, and a small-diameter ring gear mount bearing is used. As a result, the transfer is easier to install.

        A019Q4HE01
        Transfer Type MF1A
        Gear Type Hypoid Gear
        Gear Ratio 0.439
        Transfer Ring Gear The No. of Teeth 41
        Transfer Driven Pinion Gear The No. of Teeth 18
        Oil Viscosity SAE 75W-85
        Oil Grade API GL-5
        Oil Type Toyota Genuine Differential Oil LT or equivalent
        Oil Capacity Liters (US qts, Imp. qts) 0.8 (0.85, 0.70)
        Weight (Reference)* kg (lb) 15.4 (m33.9)

        *: The weight shown is the weight of the part fully filled with fluid.

      4. The illustration below shows the flow of power from the transaxle.

        A019QAEE01

  3. OPERATION


    1. The drive force is transmitted from the propeller shaft to the front housing.

    2. The 4WD ECU assembly judges whether it is necessary to send drive torque to the rear wheels based on input from various sensors. When it is necessary to send drive torque to the rear wheels, the electromagnetic solenoid is operated.

    3. The electromagnetic solenoid attracts the armature to the control clutch side. This causes the control clutch to engage and the cam to rotate.

    4. The rotational movement of the cam causes the piston to push on the main clutch, causing the main clutch to engage.

      A019PZ5E01

    5. The amount of drive force that is transmitted to the rear wheels is controlled steplessly by controlling the amperage that is applied to the electromagnetic solenoid.

    6. Accordingly, drive force from the propeller shaft is transmitted to the rear wheels.

      A019PTDE02

  4. DIAGNOSIS


    1. Furthermore, the master warning light in the combination meter assembly will illuminate and a warning message will be displayed on the multi-information display to inform the driver.

    2. For details of the DTCs that are stored in 4WD ECU assembly memory, refer to the Repair Manual.

  5. FAIL-SAFE


    1. When there is a possibility of causing damage to the drivetrain due to a malfunction in the AWD system or rough driving, the system illuminates or blinks the master warning light, displays a warning message on the multi-information display to inform the driver and stops AWD control.

      Condition Master Warning Light Multi-information Display
      AWD system malfunction Illuminates CHECK AWD SYSTEM
      Rough driving in AWD mode Pre-warning for stopping AWD control Slow Blinking AWD OVERHEATE
      Stopping AWD control Fast Blinking AWD DISABLED

      Tech Tips

      When the 4WD ECU assembly judges that the vehicle has stabilized, it resumes AWD mode. If the master warning light blinks and displays a warning message on the multi-information display, take the following actions without turning the engine off:


      • Decelerate the vehicle until the light goes out.

      • Stop the vehicle and wait until the light goes out.