This paper investigates the effect of sensor errors on the parallel parking performance of an intelligent park assist system. A path planning algorithm has been employed for generating a trajectory that maneuvers the car into the empty space in one trial. Different control schemes have been implemented for lateral steering control of the vehicle to track the trajectory generated by the planning algorithm. The control schemes include different combinations of PD and non-linear control. All simulations are carried out within the IPG CarMaker(R) and Simulink (R) environments. Positioning and sensor errors are modeled in the simulation environment and are applied to an ideal ultrasonic sensor module from CarMaker. Multiple parallel park simulations are run and the effect of these errors on the parking performance is shown with respect to the different control schemes employed.