Parking Sensors Not Working?

[Bogracer]

I have replaced one of the parking sensor units on the front bumper on my E39 5 Series, now the front and back sensors have stopped working.

Is there a reset that needs to be done?

Help!

[stringbag]

Nope. Should work first time. I have just changed one of mine and it worked fine after the swap. First make sure the fuse is ok, if so, put the old sensor back & see if it works.
My money is on the fuse if there is no noise at all. Sorry, don't know where it is!

[SpeedIsProgress]

How difficult / expensive is it to replace the parking sensors? my E46 warning noise is permanently on every time I put the car into reverse - is it an easy fix? Its doing my head in.

Alternatively is there just one fuse that operates them and I will just remove the bloody thing!

[emaps]

You need to do a diagnostics to work out which one isnt working first unless you change them all !!

[stringbag]

No you don't. They make a clicking noise when working. If you put your ear to it you should hear it. Put the ignition on, put it into reverse (or turn the PDC button on if you have one) and walk around putting your ear close to them all. The one that doesn't click or is very faint is the broken one.
Find the new part number here
http://www.realoem.com/bmw/select.do
On an E39 they come our quite easily - the trim they are attched to just pulls out. Don't know about an E46 - sorry