POWER STEERING SYSTEM

FUNCTION OF MAIN COMPONENTS

The main components of the EPS system are as follows:

Component		Function
Power Steering Link Assembly	Reduction Mechanism	Reduces the speed of the motor and transmits the rotation of the motor to the rack shaft.
	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.
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.
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.
Steering Sensor		Detects the steering direction and angle of the steering wheel assembly.
Combination Switch Assembly	Drive Mode Select	Switches the driving mode.
Combination Meter Assembly	EPS Warning Light	Illuminates to alert the driver when the power steering ECU assembly detects a malfunction in the EPS system.
	Multi-information Display	Displays the warning message to inform the driver of a malfunction in the EPS system.
	Master Warning Light	Illuminates when the warning message is displayed on the multi-information display.
	Multi Buzzer	Sounds to warn the driver of a malfunction in the system.
Absorber Control ECU*1		Outputs the damping force control condition.
Front Steering Control ECU*2		Transmits the operation angle of the steering actuator assembly to the power steering ECU assembly.
Air Conditioning Amplifier Assembly		Receives a signal from the power steering ECU assembly to limit electrical usage.

*1: Models with adaptive variable suspension system

*2: Models with variable gear ratio steering system

SYSTEM CONTROL

Component		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.
Steering Assist Control	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 (brake actuator assembly) 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.
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.

*: Models with adaptive variable suspension system

FAIL-SAFE

Fail-safe control is as follows:

Malfunction Item	Control
Torque Sensor Malfunction	Disables the assist.
Rotation Angle Sensor Malfunction	Disables the assist.
Motor Overheating	Limits the assist torque.
Motor Short	Disables the assist.
Motor Over-current	Disables the assist.
Power Steering ECU Assembly Overheating	Limits the assist torque.
Power Steering ECU Assembly Internal Temperature Sensor Malfunction	Limits the assist torque.
Power Steering ECU Assembly Malfunction	Limits the assist torque or disables the assist.
Vehicle Speed Signal Malfunction	Fixes the assist torque to a constant level.
Power Supply Voltage Malfunction	Limits the assist torque or pauses the assist (provides normal assist after the voltage recovers).

DIAGNOSIS

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.
The power steering ECU assembly will also store a Diagnostic Trouble Code (DTC). The DTC can be accessed through the use of the Global TechStream (GTS). For details, refer to the Repair Manual.