POWER STEERING SYSTEM


  1. FUNCTION OF MAIN COMPONENTS

    Component Function
    Steering Gear Assembly Changes the rotational force to lateral movement in accordance with the driver's steering operation.
    Steering Column Assembly Power Steering Motor Generates power assist in accordance with a signal received from the power steering ECU assembly.
    Rotation Angle Sensor (Built into Power Steering Motor) Outputs the rotation angle of the power steering motor to the power steering ECU assembly.
    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 Torque Sensor Detects the amount of twist of the torsion bar, creates an electrical signal based on the torque applied to the torsion bar and outputs the signal to the power steering ECU assembly.
    Power Steering ECU Assembly

    • Actuates the power steering motor mounted on the steering column assembly to provide power assist based on the signals received from various sensors and ECUs.

    • Operates in cooperation with the skid control ECU and forward recognition camera* to control the steering assist torque.
    SPORT Mode Switch Turns the SPORT mode on and off.
    ECM

    • Outputs the engine speed signal to the power steering ECU assembly via CAN communication.

    • Outputs the SPORT mode signal to the power steering ECU assembly via CAN communication.
    Skid Control ECU

    • Outputs the vehicle speed signal to the power steering ECU assembly via CAN communication.

    • Requests steering torque assist during cooperative control with EPS.
    Forward Recognition Camera* Requests steering assist torque when the Lane Departure Alert (LDA) system estimates that the vehicle departs from its lane.
    Combination Meter Assembly Power Steering Warning Light Illuminates to alert the driver when the power steering ECU assembly detects a malfunction in the EPS system.
    Multi-information Display Displays that SPORT mode is active.
    Buzzer Emits a warning sound to alert the driver when the power steering ECU assembly detects a malfunction in the EPS system.

    • *: Models with LDA system

  2. SYSTEM CONTROL

    Controls of EPS System
    Control Outline
    Steering Assist Control Basic Control Calculates the assist current and assist direction from 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.
    Voltage Boost Control Boosts the battery voltage in the power steering ECU assembly, and issues the amount of voltage necessary to drive the power steering motor.
    System Overheat Protection Control Estimates the power steering motor temperature based on the amperage and the current duration. If the temperature exceeds the standard, this control limits the amperage to prevent the power steering motor from overheating.
    SPORT Mode Control The assist characteristics are switched to achieve a suitable steering feeling for SPORT mode.
    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 (LDA) System Cooperative Control* When the system estimates that the vehicle departs from its lane while LDA system control is performed, the power steering ECU performs steering assist control according to request signals from the forward recognition camera.

    *: Models with LDA system

  3. FAIL-SAFE


    1. If the power steering ECU assembly detects a malfunction in the EPS system, the power steering ECU assembly illuminates the power steering warning light, and sounds the buzzer in the combination meter assembly to alert the driver of the malfunction.

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

  4. DIAGNOSIS


    1. If the power steering ECU assembly detects a malfunction in the EPS system, the power steering ECU assembly lights up the power steering warning light in order to alert the driver. At the same time, Diagnostic Trouble Codes (DTCs) are stored in memory.

    2. The DTCs can be read by connecting the Global TechStream (GTS) to the DLC3. For details, refer to the Repair Manual.