The parking sensors on our Discovery 3 have never worked, a previous owner had removed the fuse probably to stop the beeps. However even with the fuse fitted it still didn't beep from the rear speaker.

Reading the codes with my IID tool I saw the rear sounder (speaker) inactive and a duff parking sensor (to be replace next).

I discover that a LandRover item cost £40, whereas an identical Ford item cost me under £7. part no. in the video.