I need a low cost device (under £50 if possible) to tell me which parking sensors are not working.
There are many obd readers on the market but it is not clear to me whether or not they will test parking sensors on my 2004 XJ6.
Your advice would be appreciated.

 

Key on, engine not running, shift car in R (keep parking brake engaged) listen by each sensor for a clicking sound.

The one that is not clicking is your offending, non-working sensor. Best part, it's free!

Otherwise, the only other option is getting a Jaguar level diagnostic to read the system.

To replace, drop the rear bumper, a 5 minute job...

 

Removed bumper last month. Not straightforward as rusted bolts had to be cut off. Fitted 4 new sensors and had bumper cover resprayed. All 8 now click ok but Parking sensor system gives long alarm when starting but all 8 sensors working. Tried wd40 and power hosing to no affect. Tried to clean with very thin wet and dry paper but would not fit in gap round sensor.
Eventually found I could force thumb nail into gap and force in circle and this fixed problem. Assume problem caused by spraying bumper cover but looked fine and all 4 clicked ok.
During this nightmare I considered changing all 4 front sensors as can be obtained from China for just under £10 each.
Read many articles and there are garage obd readers using PAM (Park assist module?) technology to report on individual sensors but no info on which low cost readers have this capability.

 

Key on pos'n 2, engine off, R selected, park brake on and continuous beeeeeeep.
Remove bumper and place sensors on the aluminium bumper
with sensors horizontal ie not facing the floor.
Substitute each sensor in turn with a good one until noise stops.
If the noise does not stop you have two failures and you need two good sensors to keep
moving both around.