An electric power steering system includes a steering wheel, an electric assist motor operatively coupled to the steering wheel, and an electronic controller operatively coupled to the assist motor. A steering wheel position sensor provides an output indicative of an angular position of the steering wheel. A motor position sensor provides an output indicative of a relative angular position for the motor. Steering wheel position sensor output is acquired at each of a plurality of angular positions of the motor, thereby establishing a set of points defining a curvilinear relationship between steering wheel sensor output and motor position sensor output. The set of points is sampled to calculate a straight line which approximates the curvilinear relationship, thereby reducing periodic errors in the steering wheel sensor output. The straight line is employed to determine a position offset for the motor position sensor output corresponding to a system zero position. The system zero position is a position for which the vehicle will travel along a linear, substantially straight-ahead path.