A control system (8) for use with a bidirectional motor (10) connected to a motorized vehicle accessory to move the accessory a distance from a first position to a second position. The control system includes a detector (12) responsive to control signals emitted from the motor during rotation, where the control signals indicate the amount of motor rotation. The control system also includes a memory that stores information used to represent the position of the accessory. Additionally, this control system includes a controller (22) responsive to the memory and the detector. The controller (22) provides an output signal to operate the motor based on the distance between a first position and a second position of the accessory as well as control signals that indicate the amount of motor rotation. The controller (22) includes an adjustment routine that determines a correction factor that is applied to the output signal to compensate for inaccuracies in control signal detection.