XKR rear number plate lights not working

Good chance it is a broken wire in the wiring harness where it goes through the boot hinge. Remove the lining of the lid and you can get at the wiring. Trace the wires from the bulb holders down to where they go past the hinge. I seem to remember there are several connectors along the way so you can unplug and put a meter across.

Further to Tim091's suggestions, is it possible that you've inserted the LEDs incorrectly, bearing in mind that they're polarity sensitive? They only work when plugged in the right way round.

these were the ones i purchased

http://www.ebay.co.uk/itm/CANBUS-BULBS- ... 2eb60a7fd0

didn't know there was a right or wrong way to fit them.

i shall pop out in a sec and turn them round and see if that helps

swapping around didn't seem to work, so will have to trace the wiring

Did you ever find a fix to this? I have the same problem on my 2003 XKR. Checked wiring, checked buls and fuse. Found a series of posts on Jaguarforums.com about resetting the Auxilliary board by disconnecting and shorting battery terminas - but nothing has worked. Lookn for suggestions. Any reason why hard wiring to a tail light would not work?

ndaviesgeo said:

Did you ever find a fix to this? I have the same problem on my 2003 XKR. Checked wiring, checked buls and fuse. Found a series of posts on Jaguarforums.com about resetting the Auxilliary board by disconnecting and shorting battery terminas - but nothing has worked. Lookn for suggestions. Any reason why hard wiring to a tail light would not work?

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This thread is 12 years old now, and rtbiscuit hasn't been seem or heard of since, so unlikely you'll get a reply from him.
However, as per tim091's suggestion, my first thought would be the wiring from car to boot/trunk lid, but you say you've checked this? It runs through a conduit, and the flexing when opening and closing the lid over the years takes it's toll on the wires inside. There's a connector behind the trim panel in the boot which provides a convenient point to test continuity from there to the light units, but also to check for voltage up to that connector. If nothing there, then it is fed from the Security and Locking module under the fuse box.

Regards,
OW

If you aren't getting the "check rear lights"· message then it sounds like a fault in the security and locking module, rather than to the wiring. I would probably just do as you have suggested and run a wire to the tail lights - they come from the same relay in the first place, so its a simple fix. The only downside is you might trigger the check rear lights message, but that would be another clue to where the problem is.

Nerja said:

If you aren't getting the "check rear lights"· message then it sounds like a fault in the security and locking module, rather than to the wiring. I would probably just do as you have suggested and run a wire to the tail lights - they come from the same relay in the first place, so its a simple fix. The only downside is you might trigger the check rear lights message, but that would be another clue to where the problem is.

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On two separate XK's with broken wiring, there was no bulb failure warnings in the dash. On one of them, the boot mounted brake light was also out. The wiring was broken inside it's insulation, and in the conduit, so only found by conducting continuity tests while 'flexing' the conduit. If you check for voltage at the connector behind the trim panel, you will immediately narrow down where the problem is. If you have voltage there, it's between there and the number plate lights, and if you don't, it's more than likely in the SLM module. (The same relay feeds the SLM for both tail and number plate lights, so we know the SLM is getting that feed if the tail lights are working) Very easy to check

That's interesting, as the wiring diagram shows for all versions the number plate lights having a failure detection circuit, like the tail lights do - maybe it is a programmable option, or only used in certain territories.

Nerja said:

That's interesting, as the wiring diagram shows for all versions the number plate lights having a failure detection circuit, like the tail lights do - maybe it is a programmable option, or only used in certain territories.

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There is, or should be, as far as I can tell, bulb failure detection for the number plate lights, there certainly is for the brake light, but as said, neither car had any warnings in the dash. (I may have to pop a bulb out now to confirm or otherwise )
I wonder if there was just enough continuity through the broken wiring to allow the return of the sensing signal, but not enough to light the bulbs? The return signal for the bulb failure sensing is very low power, I believe it's measured in milliamps, so even a little copper transfer to the insulation would probably be enough to provide the required continuity?

If the number plate light power wire to the S and L Module is broken, the system just thinks the light hasn't been turned on, so gives no warning . It's when the power arrives at the module but has nowhere to go that it gets excited.
Edit! Having thought this through and while what I wrote makes sense, what I forgot is that the power wire to the S and L module doesn't pass through the notorious boot/trunk flexible conduit so is not likely to be broken!
Apologies for posting in haste!