Parking sensor problem

[jml]

I’ve had intermittent problems with the front and rear parking sensors on my C8 for a couple of years now. I presume the principal is the same on other Citroens.

Originally, when I selected reverse, it would instantly sound the visual and sound alarm of an object too close. Checking with Diagbox didn’t show any fault. That fault eventually cleared itself.

More recently the front parking has stopped completely and the rear sometimes works ok and at other times it indicates an object too close. I think this is worse when the weather is wet so I suspect it may be damp getting in somewhere. If this is the case, is there anywhere obvious ?

Progressively I have changed all sensors and the ECU but I still have the problem now.

Even when working properly, I get none of the ‘vibration’ from the sensors that some have said should happen.

Any suggestions gratefully received