POWER STEERING SYSTEM


  1. FUNCTION OF MAIN COMPONENTS

    Component Function
    Electric Power Steering Column Sub-assembly Power Steering Torque Sensor Detects the amount of twist of the torsion bar. Based on the torque applied to the torsion bar, the sensor creates an electrical signal, and sends this signal to the power steering ECU.
    Reduction Mechanism Reduces the speed of the power steering motor through the use of a worm gear and a wheel gear and transmits it to the column shaft.
    Power Steering ECU Assembly Power Steering ECU Actuates the power steering motor to provide power assist based on the signals received from various sensors and ECUs.
    Power Steering Motor Generates power assist in accordance with a signal received from the power steering ECU.
    Rotation Angle Sensor Sends the rotation angle of the power steering motor to the power steering ECU.
    Brake Booster with Master Cylinder Assembly Skid Control ECU
    • Outputs the vehicle speed signal.

    • Requests steering torque assist during cooperative control.

    Hybrid Vehicle Control ECU Transmits the ready status signal to the power steering ECU.
    Air Conditioning Amplifier Assembly Receives a signal from the power steering ECU to limit electrical usage.
    Forward Recognition Camera*1 Requests steering assist torque when the lane departure alert system estimates that the vehicle departs from its lane.
    Clearance Warning ECU Assembly*2 Transmits the simple intelligent parking assist system control signal to the power steering ECU.
    Steering Sensor Detects the steering direction and angle of the steering wheel assembly.
    Combination Meter Assembly EPS Warning Light (Red Indicator) Illuminates to alert the driver when the power steering ECU detects a malfunction in the EPS system which results in a loss of steering assist torque.
    EPS Warning Light (Yellow Indicator) Illuminates to alert the driver when the power steering ECU detects a malfunction in the EPS system which limits the steering assist torque.
    Multi-information Display Displays a warning message to inform the driver of a malfunction in the EPS system.
    Master Warning Light Illuminates when the warning message is displayed on the multi-information display.
    Buzzer Sounds to warn the driver of a malfunction in the EPS system.

    *1: Models with lane departure alert system

    *2: Models with simple intelligent parking assist system

  2. SYSTEM CONTROL

    Control Outline
    Steering Assist Control Basic Control Calculates the assist current required based on the steering torque value and the vehicle speed and actuates the power steering motor.
    Compensation Control Compensates with a force, according to the driver's steering maneuver, improving the comfort of steering.
    Brake Control System Cooperative Control Receives requests from the skid control ECU and actuates steering assist control in accordance with the operating condition of the brake control system. This facilitates the steering operation of the driver, thus achieving a high level of vehicle stability.
    Lane Departure Alert System Cooperative Control*1 When the system estimates that the vehicle departs from its lane while lane departure alert system control is performed, the power steering ECU performs steering assist control according to request signals from the forward recognition camera.
    Simple Intelligent Parking Assist System Cooperative Control*2 When the vehicle is parked in a garage or in parallel, the simple intelligent parking assist system assists steering in accordance with the signal from the clearance warning ECU assembly.
    Power Supply Voltage Drop Control When the power steering ECU detects a power supply voltage drop, it sends a load control demand to the air conditioning amplifier assembly in order to limit electrical usage.

    *1: Models with lane departure alert system

    *2: Models with simple intelligent parking assist system

  3. FAIL-SAFE


    1. If the power steering ECU detects a malfunction in the EPS system, the power steering ECU illuminates the EPS warning light (red indicator*1 and yellow indicator*2) and master warning light, and displays the warning message on the multi-information display, and sounds the buzzer to alert the driver of the malfunction.

      Tech Tips

      *1: Illuminates when a malfunction which results in a loss of steering assist torque occurs.

      *2: Illuminates when a malfunction which limits the steering assist torque occurs.

    2. If a system malfunction occurs, the power steering ECU changes control mode to fail-safe mode. For details, refer to the Repair Manual.

  4. DIAGNOSIS


    1. The power steering ECU will also store a Diagnostic Trouble Code (DTC). The DTC can be accessed through the use of the Global TechStream (GTS). For details, refer to the Repair Manual.