A method of controlling an automotive electric power steering system includes estimating a first road reaction torque from driver's steering torque detected by a steering torque detector. A second road reaction torque is estimated from the steering angle detected by a steering angle sensor. A returning torque compensator calculates a steering wheel-assisting torque from the second road reaction torque. An assisting torque is generated by an electric motor according to the result of the calculation, and is controlled in a direction to return the steering wheel to its center position. The returning torque compensator determines whether the steering angle sensor is faulty when the difference between the first and second road reaction torques is greater than a given value.