EPS(MDPS=Motor Driving Power Steering) ECU receives vehicle speed and engine RPM signal from EMS(Engine Management System) via CAN line and controls motor current accurately according to driver's steering intention. EPS ECU monitors that operating voltage supplied as IG S/W is too high or too low on "power supply terminal". If excessive high voltage or low voltage is detected, EPS ECU stops current supply to solenoid to prevent unexpected operation or damage.