Before anything, fit the O-ring spacer around the edge of the sensor membrane so that its wide side connects with the sensor housing and its narrow side points out towards the outside membrane and the back of your vehicle. After that, drop the sensor into the sensor bracket on the back of the rear bumper fascia ensuring the bracket latch parts are fully snapped into place above and below the sensor tabs, while ensuring the sensor membrane is even with the fascia. Each sensor membrane should be in the center of the openings in the rear fascia and the O-ring spacers must not be pinched. Misplacement or squeezed O-rings may result in problems with the parking assist distance sensors. After that, fit the wire harness connector back onto the sensor connector on the back side of the fascia. Put the bumper fascia back onto the rear of the vehicle for the two inboard rear parking assist distance sensors. At last, attach the negative cable to the battery and if the vehicle uses Hybrid Electric Vehicle technology, a certified technician should secure the high voltage service disconnect into the high voltage battery pack.