Parking Sensors again

Hello all. After a brief period of the system working perfectly it’s gone again. Can I check a couple of things? If just one sensor is not working does that mean that the whole system does not work? I can hear the two outer sensors clicking but the car has a tow bar and l can’t get my ear close enough to hear. As the fault is intermittent, I know that the speaker works.
I do want to try to keep the car original but there is a complete system on eBay for less money than one land rover sensor. Should I??

Well, the oddest thing. When the single “horn sound” when locking the vehicle is working then the parking sensors do not work, and vice versa. How are these two things connected? Can anyone help?
Thanks.

The single “horn sound” when locking the vehicle indicates that the alarm is not working. It means that the computer thinks a door (or bonnet or back? window) is open, so will not engage the alarm.

If it is doing this often and you believe all the doors/windows are shut, then there is a pretty consistent electrical fault somewhere. Presumably if you identify this, you will identify the parking sensor issue as it sounds like they are related. I would imagine it is a bad earth somewhere. I do not know if the girly parking is in the wiring diagrams in the Rave Workshop manual, but you could have a look. Info on downloading it here...

https://www.landyzone.co.uk/land-rover/rave-disk-maintenance-manual.260227/

Incidentally, when the alarm is in a period where its sounding the horn when you try to lock the car, does the door open led get lit on the dash when the ignition is turned on?

Also, if its a 3 door, there are sensors on the removable roof that act the same as the door open sensors to the alarm.