this is how to remove your front PDC sensors on the X3. My X3 is the M sport version so it may differ on the normal X3 so you will have to check.
Before i start anyone using this guide uses it at their own risk and i will not take any responsibility for any damage caused following it. It is very simple but if you are unsure ask me any questions or have a qualified garage perform the work.
Firstly to find a faulty sensor, turn the key to position 2 (one before starting), put the car in reverse. Now go round the car slowly and listen to each sensor, if they are working correctly each one should make a clicking sound, if not then its broke.
My broken sensor was are on the front.
To remove the front middle two sensors they are just clipped in and pull out from the front, i didn't know this so carried on to remove stuff and found this out later.
To gain access to the corner sensors i removed the front headlights.
There are four screws to remove all of them are torx head type. The first two are black and on the top of the headlight;
the second two are down the back of the headlight and are gold coloured, to get these out i used and extension bit and telescopic magnet otherwise you risk losing them in the engine bay;
Once all screws are removed, unclip the two connections that go to the rear of the light.
I also unscrewed the closest screw to the light that holds the centre kidney grill trims in place to give me more room.
I then wiggled the light around until it came out, there are a couple of clips that insert behind the kidney grill trim so i pushed the light inwards near the kidney trim then moved the light around to ensure the clips didn't snap.
Once the light is removed you will gain access to the corner PDC sensor;
and the rear of the centre ones (were the light is shining through is the whole for the centre PDC sensor);
This is how i removed the centre one, but you can see from the following picture you can just pull the centre ones out from the front as there are only 3 clips and unplug the connector;
The sensor has two clips that hold it in place and has been removed from the outer trim.
You can now replace the sensor.
To put it all back simply follow this guide in reverse and here are some random pictures that may help;
I'm sure I've missed some stuff so feel free to ask any questions.
Cheers
Ant