POWER STEERING SYSTEM

FUNCTION OF MAIN COMPONENTS

The main components of the EPS system are as follows:

Component		Function
Rack and Pinion Power Steering Gear Assembly	Reduction Mechanism	Reduces the speed of the power steering motor and transmits the rotation of the motor to the rack shaft.
	Power Steering Torque Sensor	Converts the twist of the steering torsion bar into an electrical signal and sends this value to the power steering ECU.
	Rotation Angle Sensor (Built in Power Steering Motor)	Transmits the rotation angle of the motor to the power steering ECU.
	Power Steering Motor	Generates power assist in accordance with the actuation current received from the power steering ECU.
	Power Steering ECU	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.*1
Steering Sensor		Detects the steering direction and angle of the steering wheel assembly.
Electric Parking Brake Switch Assembly*1	Drive Mode Select Switch	Switches the driving mode.
Combination Meter Assembly	EPS Warning Light (Red Indicator)	Illuminates to alert the driver when the power steering ECU detects a malfunction in the EPS system which results in a loss of steering assist torque.
	EPS Warning Light (Yellow Indicator)	Illuminates to alert the driver when the power steering ECU detects a malfunction in the EPS system which limits the steering assist torque.
	Multi-information Display	Displays a warning message to inform the driver of a malfunction in the EPS system.
	Master Warning Light	Illuminates or flashes when a warning message is displayed on the multi-information display.
	Buzzer	Sounds to warn the driver of a malfunction in the EPS system.
Air Conditioning Amplifier Assembly		Receives a signal from the power steering ECU to limit electrical usage.
Forward Recognition Camera*2		Requests steering assist torque when the lane departure alert system estimates that the vehicle departs from its lane.
Network Gateway ECU		Relays the signal between the CAN communication.

*1: Models with drive mode select switch

*2: Models with lane departure alert 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 power steering 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*1		The assist characteristics are switched to achieve a suitable steering feeling for SPORT 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.
Lane Departure Alert System Cooperative Control*2		When the system estimates that the vehicle departs from its lane while lane departure alert system control is performed, the power steering ECU performs steering assist control according to request signals from the forward recognition camera.
Power Supply Voltage Drop Control		When the power steering ECU 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 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 drive mode select switch

*2: Models with lane departure alert system

FAIL-SAFE

If the power steering ECU detects a malfunction in the EPS system, the power steering ECU illuminates the EPS warning light (red indicator*1 and yellow indicator*2), displays the warning message on the multi-information display, illuminates or flashes the master warning light and sounds the buzzer to alert the driver of the malfunction.
Tech Tips
- *1: Illuminates when a malfunction which results in a loss of steering assist torque occurs.
- *2: Illuminates when a malfunction which limits the steering assist torque occurs.
If a system malfunction occurs, the power steering ECU changes control mode to fail-safe mode. For details, refer to the Repair Manual.

DIAGNOSIS

The power steering ECU 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.