POWER STEERING SYSTEM


  1. FUNCTION OF MAIN COMPONENTS


    1. The main components of the EPS system are as follows:

      Component Function
      Spiral Cable with Sensor Sub-assembly Steering Angle Sensor Detects the steering direction and angle of the steering wheel assembly.
      Combination Switch Assembly Drive Mode Select Switches the driving mode.
      Power Steering ECU Assembly

      • Actuates the motor to provide power assist, based on the signals received from various sensors and ECUs.

      • Outputs a warning signal to the combination meter assembly when the power steering ECU assembly detects an EPS system malfunction.
      Air Conditioning Amplifier Assembly Receives a signal from the power steering ECU assembly to limit electrical usage.
      Brake Actuator Assembly Skid Control ECU

      • Outputs the vehicle speed signal.

      • Requests steering torque assist during cooperative control.
      ECM

      • Outputs the engine speed.

      • Outputs the drive mode select signal.
      Combination Meter Assembly EPS Warning Light Each of the lights and buzzers inform the driver of malfunctioning status of the system. A warning message appears on the multi-information display, corresponding to the status of malfunctions.
      Master Warning Light
      Multi-information Display
      Buzzer
      Power Steering Link Assembly Torque Sensor Converts the twist of the steering torsion bar into an electrical signal and sends this value to the power steering ECU assembly.
      Rotation Angle Sensor Transmits the rotation angle of the motor to the power steering ECU assembly.
      Motor Generates power assist in accordance with the actuation current received from the power steering ECU assembly.
      Reduction Mechanism Reduces the speed of the motor and transmits the rotation of the motor to the rack shaft.
      Forward Recognition Camera* Sends steering assistance request signals to the power steering ECU assembly.

      *: Models with Lane-keeping Assist System or Lane Departure Alert 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 motor.
    Compensation Control Compensates with a force, according to the driver's steering maneuver, improving the comfort of steering.
    SPORT Mode Control The assist characteristics are switched to achieve a suitable steering feeling for SPORT S+ 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-keeping Assist System Cooperative Control*1 When the vehicle is about to deviate from the lane or the vehicle is being assisted to keep the lane, the power steering ECU assembly assists the steering torque in accordance with the signal from the forward recognition camera.
    Lane Departure Alert System Cooperative Control*2 When the vehicle is about to deviate from the lane, the power steering ECU assembly assists the steering torque in accordance with the signal from the forward recognition camera.
    Power Supply Voltage Drop Control

    • When the power steering ECU assembly detects a power supply voltage drop, it illuminates the EPS warning light while moderating fluctuations in the steering assist torque and controls the steering assist control.

    • When the power steering ECU assembly 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-keeping assist system

    *2: Models with Lane Departure Alert System

  3. FAIL-SAFE


    1. If the power steering ECU assembly detects a malfunction in the EPS system, it lights up the EPS warning light and master warning light, and displays the warning message on the multi-information display to alert the driver of the malfunction.

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

  4. DIAGNOSIS


    1. The power steering ECU assembly will also store a Diagnostic Trouble Code (DTC). The DTC can be read by using the Global TechStream (GTS). For details, refer to the Repair Manual.