What's wrong with my parking sensors?

[lifechooser]

The cambelt snapped on my old C8, and being a slow learner, I bought another one.

On the new one, the rear parking sensors don't work. I've tried listening to them, but I can't hear any of them making any noise, so I broke out the Lexia3. It gave me the following messages;

"Permanent fault; Internal rear right hand sensor coherence"
"Permanent fault; Internal rear left hand sensor"

Am I right in assuming that 'internal' means the centre ones, as opposed to the outer two, or is it an internal failure of the sensor?
What does coherence mean here?

Basically, I need to know what I need to remove from the broken car, to put on the working one.

[GiveMeABreak]

Hi and welcome.

Yes, that is correct, those refer to the 2 innermost rear sensors.

Be aware that on earlier vehicles water can accumulate on the wiring, and run back down into the plug of the sensor, eventually causing damage. Checking that the sensor wiring is routed below the sensor plug (if there is sugfficient play) can stop the water running into them.

I had the same issues on the C5 MkII - and went through 4 of these before I decided to re-position th wiring and applied waterproof tape at the back where the plug is.

[lifechooser]

Much appreciated, thank you