Rear park assist

[threespins]

There is no search facility at the moment, so can any one help with an intermittent problem with the rear park assist. Car is an 53 plate 2.2TiD 95 estate.
The system would fail say once a month but has now got worse so it only works once in a blue moon. Are the sensors wired in series or paralell ie can one faulty sensor cause the system to fail.
When reverse gear is selected the reversing lights do come on so if that is where the supply comes from that is ok.
Any help appreciated.

[WildCards]

I'm told that one faulty sensor can cause this. Remove the sensors one at a time and see if that narrows the problem down.

[threespins]

Thanks for that. My haynes manual tells out to get at the control module and the sensors but there is no wiring diagram or test procedure so only half useful.

[Pablo16v]

The parking sensors on my 9-5 estate have just started to act up intermittently. Some days it works fine and others it starts beeping as soon as I select reverse.

[968CS]

Welcome to the club............

[JensenA]

6 months ago I bought a set of reversing sensors on Ebay, only 15 quid including the hole cutter tool, and free postage. They work perfectly, easy to fit, and look just like the originals.