One of my rear sensors had failed on my MCS
convertible and there was no clear how to guide to help me remove and replace it.
Sorry no pictures, but this should clear up a few points.
1) a failed sensor does not click when the system is working.
2) the rear bumper does not need to be removed from the car, but all the fasteners need to be removed to allow it to be moved.
3) the sensors push back to release them and push in from the back of the bumper to fit
Remove the bumper fasteners:
Two by the rear lights inside the boot opening
One under the car to the drivers side of the exhaust
One each side under the rear arch trims
One each side at the back of the wheel arch (jack the car up to make access easier)
Remove the trims behind the hinges by pushing them inwards and up.
Pull the bumper out at the top and sides
Lie under the car and pull the bumper out away from the car and you'll see the sensors.
Unclip the faulty sensor, two prongs opposite the plug, and push back from the outside of the bumper.
Remove the sensor and unplug it (it's easier to unplug it when it's hanging down)
Plug in the new the new sensor
Test to make sure all is working
Refitting is the opposite of the above.
You'll need about 30 mins in total. The job is easier that you think.
Hope this helps.
I paid £15 for the sensor and £5 for the touch up paint to colour code it. Worth a bit of DIY on a Sunday in my eyes.