POWER STEERING SYSTEM


  1. FUNCTION OF MAIN COMPONENTS


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

      Component Function
      Electric Power Steering Column Sub-assembly Torque Sensor Detects the amount of twist of the torsion bar. Based on the torque that is applied to the torsion bar, the sensor creates an electrical signal, and sends this signal to the power steering ECU assembly.
      Reduction Mechanism Reduces the speed of the power steering motor assembly through the use of a worm gear and a wheel gear and transmits it to the column shaft.
      Power Steering ECU Assembly Power Steering Motor Generates assist torque in accordance with a signal received from the power steering ECU.
      Power Steering ECU 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.
      Rotation Angle Sensor (Built in Power Steering Motor) Sends the rotation angle of the power steering motor to the power steering ECU.
      Brake Actuator Assembly Skid Control ECU Sends the vehicle speed signal to the power steering ECU assembly.
      Air Conditioning Amplifier Assembly Receives a signal from the power steering ECU assembly to limit electrical use.
      Combination Meter Assembly EPS Warning Light

      • Illuminates to alert the driver when the power steering ECU assembly detects a malfunction in the EPS system.

      • If the power steering ECU assembly detects low battery voltage, it will illuminate the EPS warning light.

      • When the engine switch is turned on (IG), the EPS warning light is illuminated in order to check the warning light circuit. When the engine is started, the warning light turns off.
      Buzzer Sounds to warn the driver of a malfunction in the system.
      Multi-information Display Displays a warning message to inform the driver of a malfunction in the EPS system.
      ECM Outputs the engine speed signal to the power steering ECU assembly.

  2. SYSTEM CONTROL


    1. The EPS system has the following controls:

      Control Outline
      Basic Control Based on the input torque signal, the motor current and motor control device are controlled to achieve the target assist power.
      Compensation Control Assist power is adjusted to improve steering feeling during steering operation.
      Electric Load Control Prevents a reduction of assist torque if the battery voltage decreases.
      Cooperative Control Brake Control System The power steering ECU assembly performs cooperative control with the skid control ECU in order to control the steering assist torque in accordance with information received from the skid control ECU. This facilitates the steering operation of the driver, thus realizing a high level of vehicle stability.

    2. Electric Load Control


      1. When the power steering ECU assembly detects a decrease in battery voltage it transmits the electric load control signal to the air conditioning amplifier assembly in order to limit electrical usage.

      2. The air conditioning amplifier assembly limits operation of the rear window defogger until the power steering ECU assembly releases the limitation demand.

  3. FAIL-SAFE


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

    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. The power steering ECU assembly also stores Diagnostic Trouble Codes (DTCs). The DTCs can be accessed through the use of the Global TechStream (GTS). For details, refer to the Repair Manual.