Parking sensors - fault finding

[b6benb6]

Ok guys, here's another one for you. While the car is out of action waiting for the rear brakes and EPB to be sorted I'm also replacing the front bumper as the current one got bruised when my gf left the car on our super steep driveway without the handbrake on.

The parking sensors haven't worked for ages, way before the car got stuffed into a wall.

As soon as the car goes into reverse there is a continuous warning tone and the PDC button flashes to indicate they ain't working, press the button and the tone stops but no PDC.

So I have decided to try and sort them out, have now got both bumpers off. Apart from some damage to the front PDC loom from the accident, it all looks OK, so how can I pinpoint the problem?

Is there a way of testing the individual sensors one at a time?

Would be gutted to replace all the sensors and then find out the problem is with the PDC control unit.

Any help gratefully received, cheers, Ben