System Outline
WARNING: This page is about a different car, the 2008 Toyota Prius. However, it is still accessible from the selected car via links, so may be relevant.
This is a system to assist the driver with steering the vehicle by reducing the required steering force. Based on the steering torque signals received from the power steering torque sensor, the vehicle speed and other vehicle information from the skid control ECU, the power steering ECU calculates the assisting current required to control the power steering motor.
If the system experiences an abnormality, the power source relay and the motor relay in the power steering ECU will be shut down and the master warning lamp on combination meter will blink. The P/S warning light will be illuminated also, resulting in the assistance being stopped.