This applies to MY2012 but should cover all facelift versions with the "newer" style parking sensors,
I looked everywhere for this info but couldnt find it so hopefully this will help others

I had a system failure meaning no sensors or rear cameras working. Initially I took this to a indi who told me I had a front left inner sensor or front bumper loom fault. I have a warranty but looms are not covered so I didnt want to pay another 2-3 hours on top of the diag to find its a loom that I can do myself so I bought a new genuine sensor (ebay £10) and went on to take the bumper off and replace the sensor - patch the loom.

The loom was perfect and tested with continuity so I fitted the sensor - No Bueno still faulty

I suspected it could be the module / wrongly diagnosed sensor or anything and hours of researching didnt help.
In the end I had the front off side headlight off, rear nearside off (to get to bumper loom connectors) and the rear nearside interior boot trim to get to he module, there are 3 plugs on the module (rear loom, front loom and the supply to car ECU)
First check you have power to the 3rd plug this confirms the fuse / relay and switch are ok.

Then start checking cont from the loom plug at the module to the bumper loom connectors.
The font loom consists of a common L and Earth then 4 yellow wires each with a different colour stripe (grey, black green and orange) it turned out my gray had lost continuity between the module and the front loom plug so either in the car under the carpets or in the engine bay. forget trying to find the breal - I ran a new cable but I will later do some further inspection of the loom to see how it has got broken to prevent further cables failing.

The system is very simple to be fair, one faulty sensor or wire will take the whole system out and these sensors cant be tested for "clicking" like the old ones they are also dead when the system is off line too so a pinger wont work either

System consists of
Front bumper loom
rear bumper loom
8 sensors
module
car main body loom (this system loom is integrated)
Dash board switch
LEt me know if you need any help diaging your system,

As soon as I made the connection, the full system worked again, no need to have anything reset etc.