I finally got in my (used) set of owner’s manuals for Harlem today. Got all 5 books (plus supps.), pouch and green leather folder for only $58 or so. I don’t know why I never got a set before now, as I usually always try to get my hands on the owner’s manual after buying a car, esp. a Jag model that I have never owned before.
Inc. in the set was a one-page supplement regarding some kind of system that sounds the usual “beep beep” warning thing when backing up, not so much to let someone else behind you know about it but to let YOU know that you are approaching such a stationary “object” so you can avoid running into it and damaging your cat. Funny thing is that ever since I have owned Harlem I never had such a system function. It does though look like the round sensors for the system are present in the lower part of Harlem’s rear bumper. Assuming she does have a (functional) system, the only thing I could think of as to why it might not operate is a blown fuse (possibly if the sensors got overly wet?). However, the supp. shows the fuse for the system to be the same (F-3) 5-amp fuse used for the car’s audio system. That would mean if the fuse were blown Harlem’s radio/cassette/CD system would also not operate, which is not the case.
Anyone have any ideas on what might be wrong? Or, is it possible that Harlem does not actually have such a functioning system? I don’t understand why the system was the feature of a one-page “supplement”, if it was standard in 2000 MY XJ8s. Why would it not just be in the owner’s manual?
It was introduced late in the x308 run. That’s why it’s in the supplement.
Common problems for it not working are the speaker failed, which is a tiny Ford part fitted under the parcel shelf trim.
Sensors do fail, however in this case I would expect a beep the first time reverse is selected.
I think the fuse stated in the paperwork maybe wrong.
The control unit has 2 connectors. black and beige.
The one with few wires has power, reverse lights, speaker. So you could check for power there.
With the ignition off and meter set to ohms, you can also check the speaker to be 50R, to save taking things apart on the shelf.
Control unit location can be pushed into the boot fusebox or behind the left light in the trunk.
I have never worked on the parking sensor system In a Jag, but i have worked on it in my daughter’s Ford. I assume it’s probably just about the same system. The little speaker that makes the “beep, beep” noise is a super common problem in the Fords. On the Fords, it’s up under the parcel shelf and a little tricky to get to.
The sensors also go out. They are cheap and easy to replace. It would be a little odd for all 4 to go out at the same time, but if you’re not the first owner, maybe they went one by one.
Not sure what the official way to test them is, but I’ve used two different ones with success. First, if any of them are still working (i.e. sometimes you hear a beep, beep) then you can put the car in reverse and stand by the corner where the sensor can’t see you. Reach over the top with something narrow like your arm or a yard stick. You want to stay in the cone from a single sensor. Come in from the top starter nd a foot or two away and move it towards each sensor one at a time. some will beep, the ones that don’t are broken.
By the way, at least on the Fords, the parking sensors work when the car is in reverse and the ignition is in the on position. The engine does NOT have to be running so you don’t have to risk getting run over.
Second method, if you think your beeper is bad, is that each sensor makes a very faint click when it’s triggered. So, if you’re very quiet, engine off but in reverse with the key on, you can again come at it from an angle around the corner where it can’t see you. Get your ear down as close as you can, and then move your hand in towards the sensor. Moving it back and forth, you should be able to hear a faint clicking if the sensor is working.
I don’t know why I never got a set before now, as I usually always try to get my hands on the owner’s manual after buying a car, esp. a Jag model that I have never owned before. 
Funny thing is that ever since I have owned Harlem I never had such a system function. It does though look like the round sensors for the system are present in the lower part of Harlem’s rear bumper. 
Assuming she does have a (functional) system, the only thing I could think of as to why it might not operate is a blown fuse (possibly if the sensors got overly wet?). However, the supp. shows the fuse for the system to be the same (F-3) 5-amp fuse used for the car’s audio system. That would mean if the fuse were blown Harlem’s radio/cassette/CD system would also not operate, which is not the case.