Originally Posted by Adam Lueb

I did some more checking of the back up sensor. My son parked his car in back of mine. I turned the key to the start position and the shifter to reverse, the alarm sounded, as he backed up the sensors beeped until he was far enough away they stopped. I had him pull the car back to the original position in back of my car and this time I started the engine, foot on the brake and engaged reverse no sensor noise at all. Not even the three beeps the owners manual says will sound if they are not working. What's up with this?

Originally Posted by Thermo

Adam, what you want to do is to set the E-brake when the backup sensors are not working and have the car in reverse (it is preferable if you can get the rear tires up against the curb as you will see). Now, with the backing system engaged, you will need to get out of the car and put your ear near each of the 4 back up sensors (little flat spots on the bottom edge of the rear bumper. What you are looking for is them to be emitting a high pitch clicking/squeal sound. If you can hear that, then that sensor is working. If 3 out of 4 are working, then the one with no sound is your bad sensor. If none of them are making noise, then odds are your backup module is toast or you blew the fuse for the system. If all 4 are clicking/squealing yet you don't get the beeping sound, then odds are the speaker in the backup module (yes, the speaker is built into the module) is toast.

Hope this helps fix your issue.