Evening all , I have just replaced rear right corner parking sensor with new one as that is the one that was registering a fault , diagnostic tool has cleared fault and no new faults are found yet my parked my aid is still not working , anyone any ideas please

All sorted now, removed bumper and belled out harness , was a dodgy wire to sensor

According to GAP tool my rear sensors are detected but fronts arent , can you tell me the sequence of belling out the harness , I get 12.5 n brown feed wire to plug behind the front headlight , earth is quite high resistance , do you also know where it might be sourcing its earth please .

Although I can separate front to back , it doesn't allow rears to work on their own.

I think the earth is from the ECU in the rear.

If you do a CCF edit to change sensors to rear only. And disconnect the plug under headlight, the rears should work

I think I tried that , but will give it another go as I was trying to remove dipping mirrors when reversing in CCF and it said update failed. However that's resolved so will enter that sensor separation again.

Thanks much appreciated.

Ah ok , thanks will try that again , Thanks for your reply.

So now I have rears working separately and fronts disconnected,.

Is there a belling out(con check)that I can detect which front is faulty. Ive forgotten what I did before. Only 10 mths ago I replaced two of these before , perhaps I need to change manufactures!

So I have checked out resistances to each front sensors via the plug pins from behind the headlight (drivers ) , the results have not identified the culprit. All sensors have around 10ohms by probing between the main power feed (brown) to each colour associated to each sensor.

The black earth wire is showing a high resistance and according to the wiring diagram this goes back to the Parking Module . I would thing its earthing mount is the same as a heap of other earths in the left rear.
Not moving forward at the moment.

Have you carried out a continuity check between pins on large plug behind headlight and pins on each sensor ? If you are showing high resistance between the earth pin on large plug and all 4 sensors pins that could be your issue . You could also try checking between earth pins on each sensor plug as they should be common . The faulty wire I found on mine had no visible signs of damage but very high resistance ( virtually open circuit .

OK , I read with interest on this one , I take it your asking to to check earth connections between sensor plugs back to male joint behind light.
If so , I need to get bumper off , no problem , it would maybe make an answer, I cant believe that this has suddenly exposed itself which has cancelled rears so much.

I have now checked continuity with all four front sensors and with each wire back to the plug at the rear of the headlight. They test out with no broken wires . Also checked wires back, earth, live , and four sensors to P module, they are all sound as a pound! Only thing left is sensors themselves.

Oh man , what a work for just one sensor!

A common fault is one of the 8 sensors having low resistance between the black and brown wires.
This will take down the whole system and 2’power fault codes will be registered.

A sensor can also register an object continually. No electrical test or fault code will show this. You just get a continual beep. Live readings will tell you which one. The one that says 0 meters.

Sensors can also fail and a specific fault code will be provided.

First diagnostics threw me that no fronts were detected . So , that what was the route that there was a total failure , as you say both front and rears showed diagnostic failure . Having swapped the two fronts that I had access to without the bumper off and armed with three new sensors , the middle two were left. I could have saved some trouble by testing the middle two first once I had the bumper off, but hey ho the wiring is spot on ..... a red herring!
I did find the culprit very wet in the bumper holder , thus creating fault , but drying it out and trying again it was already corrupted. A genuine sensor as well.

Not entirely intuitive as to how you single out ,Yes , but many thanks , its good to get support !