POWER STEERING SYSTEM

FUNCTION OF MAIN COMPONENTS

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

   Component			Function
   Steering Column Assembly	Power Steering ECU Assembly		Actuates the power steering motor assembly mounted on the steering column assembly to provide power assist, based on the signals received from various sensors and ECUs.
   	Power Steering Motor Assembly		Generates assist torque in accordance with a signal received from the power steering ECU assembly.
   	Rotation Angle Sensor (Power Steering Motor Assembly)		Outputs the rotation angle of the power steering motor assembly to the power steering ECU assembly.
   	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.
   Brake Actuator Assembly		Skid Control ECU	Outputs 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.
   		Multi-information Display	Displays a warning message to inform or warn the driver of the system condition in accordance with signals from the power steering ECU assembly.
   		Buzzer	Sounds to warn the driver of a malfunction in the system.
   ECM			Outputs the engine speed signal to the power steering ECU assembly.

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.
   Inertia Compensation Control	Ensures the starting movement of the power steering motor assembly when the driver starts to turn the steering wheel.
   Recovery Control	During the short interval between the time the driver fully turns the steering wheel and when the wheels try to recover, this control assists the recovery force.
   Damper Control	Regulates the amount of assist when the driver turns the steering wheel while driving at high speeds, thus damping the changes in the yaw rate of the vehicle body.
   System Overheat Protection Control	Estimates the power steering motor assembly temperature based on the amperage and the length of time the amperage has been applied. If the temperature exceeds the standard, it limits the amperage to prevent the power steering motor assembly from overheating.
   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 battery voltage decrease, 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.

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 in the combination meter assembly to inform the driver.

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.

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.