Vehicle steering system

A vehicle steering system, comprising:

• a steering actuator including i) a two-system electric motor having a single motor rotation shaft, ii) a steering rod connected to a wheel and configured to steer the wheel by a steering amount corresponding to a motion amount thereof, and iii) a motion converting mechanism configured to convert a rotating motion of the single motor rotation shaft into a motion of the steering rod in the motion amount corresponding to an amount of the rotating motion;
• a first motor rotation angle sensor and a second motor rotation angle sensor provided so as to respectively correspond to the two systems of the electric motor and each configured to detect a motor rotation angle that is a rotation angle of the single motor rotation shaft;
• a steering amount sensor configured to detect, as the steering amount of the wheel, the motion amount of the steering rod or a motion amount of a movable member in a case where the steering actuator includes a movable-member moving mechanism configured to move the movable member in the motion amount corresponding to the motion amount of the steering rod;
• and
• a controller configured to execute a steering amount control of controlling the steering amount of the wheel by controlling an operation of the electric motor,
• wherein the controller is configured to perform detection-value inappropriateness determination in which it is determined that any one or two of a detection value of the first motor rotation angle sensor, a detection value of the second motor rotation angle sensor, and a detection value of the steering amount sensor are inappropriate based on comparison among the detection values.