Backup sensor - solid tone every time - how to fix?

[Dobbler]

I've done more than a dozen searches and come up with at best partial information on this problem.

When I put the car in reverse, I get the solid warning tone. No beeps, just the solid tone.

I suspect wet weather and/or washing the car may have introduced the problem. How to diagnose? What may be the fix? Do I have to pull the sensors out of the rear bumper (how?), or are there connectors elsewhere that may be wet? I can't for the life of me find any photos for a B8.5 A4/S4 showing locations and how to remove. Don't want to go busting plastic fasteners and whatnot.

[Joker S4]

It's possible that one sensor is disconnected somehow, or one is extremely dirty. I had this happen and it was resolved by cleaning with a basic detail spray. The sensors are the little circles on your bumper, might have to take the bumper off to get behind there.

[Dobbler]

It's possible that one sensor is disconnected somehow, or one is extremely dirty. I had this happen and it was resolved by cleaning with a basic detail spray. The sensors are the little circles on your bumper, might have to take the bumper off to get behind there.

Thanks - they are body colored so are the sensors painted, or is that a plastic cover over the top?

[jsh139]

I got this same thing intermittently over the winter. With all the salt and crap on the roads, I just assumed it was dirt. I have the parking graphic turned on, and it was always just one sensor that was freaking out. After I wiped it off, the solid tone would go away. No idea if that was a fix or it it is starting to actually fail. Let us know if you find a cause/fix for it (assuming it’s not just dirty).

[Dobbler]

I gave each of the 4 sensors a whack with my hand and all seems well again...............for now.