CJ - I would suspect that surface mount transistor (If you have a test meter you can do the collector, base, emitter "diode" check assuming it's not an FET type) - I suspect those brown thingies are small value capacitors) the blue units could be small value resistors - hard to tell (they could also be diodes) sometimes surface mount resistors have a value printed on them.

If you know an electronics tech he may be able to diagnose and fix the unit - I've swapped out surface mount components with success without any special soldering equipment - I often stole the parts from another board that was junk.

Mac.

Edit - looking at the copper foil that doesn't look like a transistor - possibly a diode of some type, it definitely has to allow current flow. So try doing a diode/continuity check across it.

 

Really don't think it's a field effect, don't see why it would be.
ANYWAY, I replied to all this on that other thread. My bad for posting on two established threads anyway.
As in that other thread, CBE has zero continuity everywhere, so evidently toast.
I'll continue in the other thread and let this one die.
Post #13 https://www.jaguarforums.com/forum/x...orking-144436/
Yeah, can't see how two pins on one post would work out for a transistor. Weird though.

 

Is this statement true? 2010 and up are totally different than 07 to 09 in regards to wiring...10 and up have some sort of suppressor that can fail? Don't see it on my 07

 

Top tip: Cut the heat-shrinked insulation around the board only from one side of the circuit board, and then twice across the board (not too deep!), so the insulation can flip open to towards the non-cut side.
Once ready, you can then simply fold back the insulation to close it again and wrap some electrical tape around it all to water-seal the insulation.

The "surface mount transistor" mentioned above is actually not a transistor, but two diodes in parallel into a single packaged unit (BAV74).
These diodes are doubled, since a single one cannot carry the current to light up the LED brake light bar.

When the brake light bar does not work at all or when it does not show the full power, this double diode unit could be faulty.
You can easily use the diode check on your multimeter to check continuity.

Plus of your multimeter should be to one of the two inputs to the block (the anodes of each of the double diodes).
Minus of your multimeter should be to the single output (the cathode).

Replacement: You can use a single, higher power diode, eg. 1N4002. I used a power-supply side 1N4007 diode, which I de-soldered from a defunct electronics board.
Such a diode can take more current than the original BAV74 twin diodes, so it will live a lot longer.

The bright ring on the diode (the cathode) should point towards the big 220 muF capacitor to ensure continuity.
You will need to bend the legs a bit to contact the solder points on the board. Make sure not to short-circuit anything.

After mounting, of course check again!

Working aid: About diodes.