Have been attempting to resolve this issue on my recently acquired 2006 X-Type Wagon over the holidays with no success.

Situation: ALL exterior lights on the vehicle operate correctly except the LH Stop/Tail light. (To clarify, neither the Stop light filament nor the Tail light filament function). In the X-Type Owner's Manual, this bulb is denoted as Number 2 in the section titled, Rear Light Assembly - Wagon.
Attempted Fixes:

• Changed the Bulb - Replaced the existing bulb (which did not appear burnt out) with a P21/5W bulb purchased from AutoZone. Problem not fixed
• Inspected the bulb holder for corrosion and or damaged fittings. None found.
• Inspected wires going into bulb holder for wear or damage. None found.
• Followed a wire harness out of the tail of my wagon to where it appears to connect to another harness under the rear seat (pulled the cushion) to see if I could detect any damage or lose plugs. None Found.
• Next, considered the possibility of a bad fuse. But, which fuse? Reading through the list of circuits covered by each fuse in the Owner's Manual, I could not find a fuse clearly identified with the Stop/Tail Light or even the Tail Light Assembly in general. The only fuse that might be a possibility was F47 (Passenger Compartment Fuse Box) which covers LH side (parking) lights. But, which lights were considered "parking" lights? Again, referencing the Owner's Manual, I found "parking" lights defined as "...front sidelights,tail, number plate and any other marker lights required by local legislation." So, if the LH tail light was only one of a handful of lights covered by this fuse (F47), and all the rest of the lights worked, then it would seem the fuse is not the issue.

At this point I have some questions:

1. In the Owner's Manual, it cautions that when changing out a bulb "fitment of the correct type is essential." At first glance you would think this refers strictly to the bulb type i.e., replace a P21/5W bulb with a P21/5W bulb. But is that enough? Do some P21/5W bulbs have different contact points that better accommodate the Jaguar bulb holders? Although you would think there is a universal standard, I feel I once read that not all bulbs work in Jaguar bulb holders.
2. I considered at one point that I might have an issue with the Brake Light Switch but dismissed this as a possibility since the Tail light did not work and the Brake Light Switch had no impact on the Tail Light. Am I correct in dismissing it?
3. Where am I making incorrect assumptions? What have I "goobered up'?
4. How should I proceed?

Thank you for letting me brainstorm this.

As always, any assistance is appreciated.

 

The only commonality that remains is the common earth to that tail light assembly, but if you have lost that then you would also be missing the indicator and reversing light on that side as well.
Can you quickly remove and plug in the right side cluster to the left plug, to just test that you don't have a fault internally within your left cluster?

 

Can do. Will get to it later today. Thank you and Happy New Year.

 

Well, that took awhile to get around to addressing my Tail/Stop light issue. Unfortunately, life got in the way.

Anyway, taking off the left tail light assembly was more involved than I thought. To access its retaining screws, required removing the electronics rack -- my hands were too big to squeeze in between the rack and the tail light assembly -- and that required other things to come out first. So, I decided to take one more look at the Tail/Stop Light bulb holder before undertaking all that work. One of the contacts in the holder seemed a bit "flat" so I "arced it up" with a very small screwdriver. When I re-inserted the new bulb, it worked. So, issue resolved.

Thanks for all the ideas.

 

A few years ago someone posted on this forum a forensic engineering description of our tail/stop light circuits after he had replaced tail light bulbs too frequently. I forget the details but I remember the conclusion was in fact an undersized ground/common wire to the tail light. As tail light or as brake light the circuit was fine but when both were powered at the same time the thin ground wire heated up. Usually the heat conducted through the wire to the bulb shortening the bulb life. Often it caused a hot spot at the connections in the bulb socket causing accelerated corrosion there. I have replaced that bulb 3 times in the years I have owned the car which is 3 times as many as all other bulbs in the car combined.