Reverse lights not working,bulbs and fuse good? Thanks for any tips.
Gordon,
If other lights served by the rear BFMs are working (e.g tail lights, licence plate lights L&R indicating grounds OK) and the battery supply fuses (A7 in LH fuse box and B7 in RH fuse box) as well as Ignition Switched power fuses (numbers 2 and 1 in centre fuse box) are good then the problem must be in theTransmission Rotary Switch (TRS)or the wiring/connectors between it and the two BFMs.
There is a 24-way Yellow connector under the centre console ski-slope panel which serves the TRS which grounds the Slate/lime green wire through pin 8 to energise the reversing light relays in both BFMs to switch those lights on.
With the ignition switched on, if you ground that Slate/lime green wire both reversing lights should illuminate.
If not, check for continuity on that Slate/lime green wire between pin 8 of that connector and pin 2 of the 15-way Black connectors at each rear BFM.
Thanks Bryan, will do and report back, all other lights working 
Hi Bryan, itâs got to be the TRS, where is this located
Gordon,
So when you manually grounded the Slate/lime green wire as I described the reversing lights came on?
And you have continuity from pin 8 on that Yellow connector under the ski-slope all the way back to the BFMs?
Here you go -
Yep, lights working after grounding, will remove TRS and see if I can get into it to check contacts., would this be the next step Bryan ?
Gordon,
It may be that the TRS is badly adjusted so that it doesnât know that the tranny is in reverse when the gear selector lever is in âRâ. I canât remember the procedure for âadjustingâ the TRS (having never done it) but perhaps someone who has don that can advise the procedure
Doesnât the dash show âRâ when you select reverse?
Thanks, will try moving gear selector slowly from P to D to see if we get a flicker of light.
No flicker, didnât realise gear selection came up on dash,it lights up next to gear stick in red but not on dash, my car is a 91 Daimler, maybe different in that regard to other year model XJ40?.
You may be correct. The gear position lights up on the dash on my current car (Range Rover) but I canât remember if it did that on my '91 Jag.
However, presumably if on your car the âRâ lights up when the tranny is in reverse, that signal must come from the TPS so it knows that the tranny is indeed in reverse and therefore it should ground the Slate/light green wire to switch on the reversing lights? You did check continuity on that Slate/light green wire from the Yellow connector under the ski-slope back to the rear BFMs?
Bryan - Not sure about this, but I think the bulb under the indicators on the tranny selector is always lit and just masked by the various apertures (P R N D) as it passes through those relative positions - I donât think it actually lights on each position through any kind of âindependentâ switching âŚ
Larry,
Yep, that makes sense - a much more elegant Jaguar solution! 
So the problem may still be the TPS or itâs âadjustmentâ then?
Just wondering,rear fog lights not working, are reverse lights on the same circuit ?
Gordon,
IIRC, for the rear high intensity fog lights to illuminate, the engine has to be running and/or the headlights have to be on low beam.
Are they?
Just tried that Bryan, engine running, lights on low beam. Rear fog lights not on.
As far as I can see from the circuit diagrams, the only commonalities betwen the rear fogs and the reversing lights are the fact that they are both powered through the same fuses I identified earlier via adjacent pins in the 15-way black connectors at their respective rear BFMs But it would be too much of a coincidence to think that both sets could fail at the same time.
Of course they both are goverened by the lighting logic unit in the switch pack which dictates when they can be illuminated as dictated by the Jaguar gods. Never heard of a problem with that.
Ok, grounded lime green/slate wire under ski slope, nothing,re checked all fuses left, Right, centre, check bulbs, connectors.Is there a relay somewhere im missing? All fuses good, still no reverse lights or rear fog lights,last resort for reverse lights is the TRS, but foggies? Ahh I will persevere as long as it takes, this process of elimination, thanks for your help
WAG here but sometimes the fuse boxes have cold/cracked solder joints, across fuse tests good but output at harness on back no good.
Worth a check as a last resort maybe?
Larry makes a good point about the possibility of âdryâ solder joints in fuse box.
However, if the battery voltage fuses (A7 Left and B7 Right) were not passing power for whatever reason, then in addition to the reverse and rear fog lights, the rear stop and turn signal lights wouldnât illuminate either - do they?
Yes,turn/tail/stop lights all working.