Very strange yes. Have you tried disconnecting the battery for some time and connect again? Hard reset we know solve many problems.
Also, does it continue to give you warning if you put in reverse and turn Off and On Parking Assistance using a button above your head?

 

That's a good idea, I can't remember if there fault occurred after installing the new battery or not, so I'll give this a try. If I'm in reverse and switch of parking assist the error still shows.

Thanks!

 

Water got into my parking sensor ECU in the boot (RHS behind trim), corroded the connetions. Worth checking.

 

Will check, thanks for the tip!

 

So it turns out it was a faulty sensor after all... Eventually it stopped clicking and once it was replaced everything worked ok. Removing the rear bumper was a pita - as was getting it back on again!! And now... I have a number plate light error lol! I imagine that requires the bumper coming off again....

Thanks for your help everyone, massively appreciated.

 

I'm doing the same job tomorrow on my SW (even worse than on a saloon apparently ).

I know that it's one of the central 2 sensors that's gone from Multiscan results and that it is possible to do these without removing the bumper if you've got small hands but I'm not sure exactly which of the 2 it is and with the bumper off it gives me the opportunity to more easily fit a number plate light reverse camera to hook up to the android HU and also mudflaps when I'm re-assembling - both of which have been sitting on the shelf for a few months now.

Did the front bumper a couple of days ago to fit a new lock (microswitch and handle gone on the old one) and replace the pitted grille - gave me a chance to also remove, copper slip and replace the undertray fixings whilst I was there.

Claiming to SWMBO that spending a few days under the car over Christmas is good rehabilitation exercise having had a stroke just over a year ago (resulting in having to swap from a 1.9 Ti manual SW to a 2.4 Ti Auto SW).

 

I'm doing the same job tomorrow on my SW (even worse than on a saloon apparently ).

I know that it's one of the central 2 sensors that's gone from Multiscan results and that it is possible to do these without removing the bumper if you've got small hands but I'm not sure exactly which of the 2 it is and with the bumper off it gives me the opportunity to more easily fit a number plate light reverse camera to hook up to the android HU and also mudflaps when I'm re-assembling - both of which have been sitting on the shelf for a few months now.

Did the front bumper a couple of days ago to fit a new lock (microswitch and handle gone on the old one) and replace the pitted grille - gave me a chance to also remove, copper slip and replace the undertray fixings whilst I was there.

Claiming to SWMBO that spending a few days under the car over Christmas is good rehabilitation exercise having had a stroke just over a year ago (resulting in having to swap from a 1.9 Ti manual SW to a 2.4 Ti Auto SW).

You can check which one is faulty by listening closely, put in reverse without starting your car, and listen which sensor is clicking, the one thats silent will be faulty

 

I was getting the "park assistance not available" error message and noticed that even when in reverse without running none of the sensors were vibrating (also not vibrating when running in reverse with wife holding the brake down). I assume that the error with one sensor had resulted in a complete shut down of the system - don't know whether this is normal on an auto with front and rear sensors when one sensor goes?

Once I had the bumper off earlier however it was a simple job of swapping a "new" sensor into place (of course it was the second of the two centre sensors I tried that was faulty). Reverse camera also fitted and tested (need to properly run the cables in the cabin later) along with mudflaps and new wheel centres to replace the e-bay specials that were on it - slowly getting this one up to the standard of the manual I had to let go.