Patent ID: 7444217

Claim:
An electric power steering system comprising: primary and secondary torque sensors for detecting a steering torque applied to a steering member; a difference calculator that calculates a difference between detected torque values detected by the primary and secondary torque sensors a predetermined number of times in such a state that a predetermined steering toque is applied; an average value calculator that calculates an average value of results of calculations made by the difference calculator; a threshold value corrector that corrects a threshold value based on the average value calculated by the average value calculator; and a failure determining unit that performs a failure determining operation for determining whether or not the primary torque sensor fails based on a result of a comparison between a difference between detected torque values detected by the primary and secondary torque sensors and the corrected threshold value is performed during an assist control operation in which a steering assist motor is controlled to be driven based on a detected torque value detected by the primary torque sensor.