What's inside a parking sensor and why do they go bad?

Isolate a bad sensor by listening if it has an audible click while in reverse. If there is no noise check the connector...swap it with another one to determine if its the sensor or the circuit that's bad...im my case it was the sensor and i cracked it open to see why it failed and it was due to water intrusion and corrosion.

[@CigRacing]

Very cool Ed. Thanks for posting. I have to go through this troubleshooting process as well on my '06 4.4 HSE Rover. I haven't attempted changing out any of the sensors yet.

[@productreviewspecialist]

Im glad this video can help you. One other reason a sensor can fail is due to being painted over. Were you able to fix your issue?