POWER STEERING SYSTEM CONTROL POWER STEERING CONTROL

  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 outputs 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 Motor Assembly

      Generates assist torque in accordance with a signal received from 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.

      Brake Actuator Assembly

      Skid Control ECU

      Sends the vehicle speed signal to the power steering ECU assembly.

      Air Conditioning Control 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 ignition switch is turned to ON, 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.

      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

      Calculates the assist current from the steering torque value and the vehicle speed, and actuates the power steering motor assembly.

      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.

    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 control assembly in order to limit electrical usage.

      2. The air conditioning control 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.