Reversing sensors

[gray99y]

Hi all, my A4 avant Quattro has developed a fault on the reversing sensors. One of them is indicating that there is an object there but there is nothing. Thing is when it rains or just after a wash, it works fine.
Any ideas?

 

[ruairi83]

Hit them with power hose incase dirt lodged between bumper and sensor

 

[jdp1962]

And if that fails to fix it, it might be worth getting the car scanned with VCDS.

 

[GeoffDunk]

I used to find car wax got lodged in the X5 sensors after clenaing the car causing the same problems, high pressure wash used to clear it and/or and air line.