ok Iam looking to get a few small niggles sorted on the m5 before i sell it and top of my list is the PDC ,

it works very occasionally but most of the time it just flashes the light and a pdc failure comes up on the dash ,

I do have a sensor on the front bumper that looks like its hit something so thats the focus of my concern ...

ive 2 questions ...

1 . is it true if i turn on the ignition and put it into reverse and listen very very closely to each sensor i should hear one thats not making a ticking noise ? i know the bmw diagnostic can pin point the exact sensor but taking it to a dealer for this really isnt realistic... am i on the right track ?

2 . has anyone on here any links / recommend somewhere to buy replacement sensors ? other than the main dealer again of course

Thanks in advance