You should remove the front fascia, disconnect the sensor harness, remove the sensor from the sensor housing, paint the sensor housing and apply structural adhesive epoxy, Lord Fusor (TM) 127EZ or equivalent, to the fascia at the mating surface. Then, you should install the sensor housing to the fascia, allow the adhesive to cure according to the manufacturer's directions, install the sensor to the sensor housing, connect the electrical harness and install the front fascia.