2003 XJ8 brake light

Something strange happened on my way to the forum.
The right brake light of my 2003 xj8 stopped working. Not the left one.
I swapped the bulbs. Still not working on the right but working on the left.
Not the bulb.
Upon investigating a tad, it seems that the bulb does not receive the proper voltage.
Has anyone ever encountered this ?

Also, I just noted that the driver seat begins to tear. I will have to change it. Does anyone know where I get the seat color references ?

My guess is that you have an earth problem.

If the problem is not a simple electrical problem for the brake lights, then it may be a problem with the circuit board that powers the brake lights. See this:

As for the interior color codes, use the search function in the upper right hand corner to find on this site a listing of the three letter color codes and the name they map to. With that you will have a reference to the shade needed to match what you have now.


Oh many thanks, that is very valuable.
Yes I assumed that it was the control module.
As one of the brake lights still works, I wonder if I will not try to connect the bad one in parallel with the good one.

Ah thanks
I do not think so because the earth is common to the whole right rear light module and the other lights work
Still investigating.

If you have the X308 2003MY XJ8 then I will guess the SLCM output semiconductor has failed!!!

If you have the X350 XJ8, you will need more diagnosis.

Thanks; still investigating. It looks like the nightlights are off (both sides) too.
Only the rearing lights work on both side.

On the idea of powering both brake lights off one circuit (chip) - I would be concerned that the extra load might cause the other brake light power chip to fail prematurely.

Since these failures are well known it doesn’t seem like these chips are overbuilt for their purpose - it could be doubling the load may push them over the edge.

This would be especially true if these chips are failing due to heat. I can’t recall if anyone has determined the actual failure cause within the dead driver chips.

I would almost suggest, if that were the desired course of action, to use the brake light chip output to drive a relay and get the power directly from a 12v power output somewhere else.


You should take a new feed from the 3rd (window ) brake light. This is driven off a relay in the trunk fuse box.

The wire will be handily available in the fuse box on the yellow towbar connector

Night Tail lights are driven off the bcm above glovebox.
Wise to check earths etc if so much wrong

Right you are
Or I could replace the incandescence bulbs with LED bulbs, as they have a far lower impedance.
Anyway. I have a diagnostic tool. I just recalled.
I will try running it today to see if I get any error codes…

Not sure of the benefit of LEDs. You’re going to have to do a wire adjustment whatever.

Without fixing the security module, I suspect you will have a dash error message, bulb out.
Adding LEDs will only make this worse. It will complain about the tail lights too.

Yes I would have the dash error message with the LEDs, correct. The rationale was that at least I would have both brake lights.
Anyway the rear night-light are also gone apparently so I may have to consider buying a module sooner than later.

As previously said the night lights are driven from a module inside the car by the glovebox.

Again, you could bodge them off the yellow towbar plug in the fusebox.

So I did a quick fix.I am investigating how to change what module.
In the meantime I have wired the rear night-lights (also dead) to the side night lights, which are powered by a relay.
The dead right brake light, I used the left brake light, which was easy to get.
Advienne que pourra.

I love it when a plan comes together…