Further info:

As I just found out, the "X300" SLCM-s came with 2 different PC boards, with 3 chips or with 5 chips. Possibly early and later. So, it appears that the type of PC board is not related to whether it is an "X300" or "X100" SLCM but that it was just a change in PC board design having the same pin functions.

 

Here is an image of the chips referenced above. My eyes are having trouble discerning anything amiss with the chips. Here is the best photo I can do:

They look good to me, but how to test the connections to the board?

 

So, I disconnected the 16 pin connector at the SLCM, then did a continuity check on the OY BT1-3 wire to the OY on the tail light assembly connector. It checked good continuity.

I tried to do it with the connector connected to the SLCM (OY) but got continuity to every wire at the tail light assembly. All that did was confuse me.

 

Do the following tests:

1. On the bench, check for continuity between the SLCM pin to which the OY connects and the leg of the chip marked on the pic.


If you get continuity, it will confirm that this is the chip controlling the Right Stop Light and that the link on the PC board from the chip to the OY output pin is good.

2. With the car battery, SLCM and the plug at the right tail light all disconnected, check for any continuity between the OY and the ground (to eliminate any short to ground of the OY wire). If no continuity to ground, plug only the connector to the tail light. Using an external battery (or power supply), via a 10 Amp fuse just in case, connect positive to the OY pin/socket of the connector for the SLCM and negative to ground. The right stop light should light-up.

3. With the car battery still disconnected, disconnect the plug from the tail light and plug-in the open SLCM. Check for continuity between the leg marked on the above pic and the OY at the tail lamp plug.

4. With the open SLCM still connected, connect the car battery and switch the ignition on. Check whether there is 12V on the point of the chip marked on the picture below.


Let us know your findings.

 

Oh, my gosh! The detail of this troubleshooting is magnificent. Thank you ever so much.

I will get my son out to the barn with me this afternoon after school and work and give it a go. Will post results.

 

several 308 exclusive parts are tagged as 300, diff assembly comes to mind. you’d probably have to work at coventry to figure out how part numbers were assigned

 

Question SLCM Test Results - 2001 X3081. SLCM disconnected case open - Continuity from SLCM connector OY to SLCM relay chip leg 4 as marked; continuity yes
2a. Disconnected from SLCM and light assembly; OY checked from SLCM connector to ground; continuity no
2b. Disconnected from SLCM and light assembly; OY checked from light assembly connector to ground; continuity no
3a. Disconnected from SLCM; external power applied to SLCM connector OY and ground; the correct filament lit up
4. SLCM connected case open, car battery connected, ignition on position 2; 12V sensed at each of the three relay chips

I'm grateful you are sticking with me! I think I did the tests correctly, so where are we now? What next?

I posted this response on the wrong thread. Sorry for the duplication.

 

Last test:

With the SLCM open and everything connected, check the voltages on the pin marked on the picture when the brake lights are "off" and when they are "on". When the brakes are "off", there should be no voltage on the pin or there could be some small voltage. When the brakes are "on", you should see a voltage of some 5V or 12V or some in-between. If there is no such voltage on the pin with the brake pedal pressed, then the problem is not in the chip but elsewhere in the SLCM. If, however, you see a voltage change to 5-12V on the pin (but the right stop light does not come on), then the problem is in that chip and it will need to be replaced.



The replacement chips are BTS409L1E3062A (also called BTS409L1in TO-220 housing) and you can get them from an Ebay USA seller - https://www.ebay.com/itm/BTS409L1-TO...kAAOSwnbZYDPHU. I suggest you get 3-5 for spare as these chips are no longer manufactured and may become NLA soon, You can get them somewhat cheaper from some China/Hong Kong sellers but it would probably take very long time to get them from there.

There are two ways to remove the chip:

1. Soldering iron - cut the 4 legs close to the chip with small wire cutters, heat the chip's heat-sink plate on the other side and carefully lift the chip (do not force as it may damage the PC board trace under the chip, make sure the tin has melted), unsolder the 4 cut-off legs from the board.

2. A better way is using a small controlled hot air gun (resoldering station) to heat the whole chip until it can be moved away.

If you are not confident to do it yourself, you should be able to find an electronics repair shop to do it for you.

 

Here is an update for you all; especially M. Stojanovic! Thanks to all of you for your patience and diligence, and mostly thank you M. for being spot on with the diagnostics. I would not have been able to resolve without you guys!

Jolene is on the road again! This is how:
1. Troubleshooting down to the chip/circuit board layer continued using the forum member suggestions; determining that M. Stojanovic was spot on! The leg of the chip controlling that right brake light was not passing voltage through. The suggestion of using external power to test the circuits proved decisive.
2. Not comfortable with my soldering technique, ordering (eBay) a replacement SLCM being careful to match the same number (from the yellow label LNG2600HB) as the original module for about $200USD. I willingly paid premium for a tested unit from high rated feedback vendor. I did not look for the VCATS label else where in the trunk as mentioned. Perhaps I should have, but my logic dictates that the module model numbers were the actual determining element. This proved out.
3. With the replacement SLCM installed, the light became active again, thus resolving the issue. Seemingly nothing else went wrong while poking/prodding/testing connectors and wiring harnesses. Reassembly easily accomplished.
4. Programming the remote entry key fobs remained. That went easily and smoothly.
a) Hold the brights on, turn the key on.
b) Release the brights, then flash them five times.
c) Press any button on each fob to total five fobs. I have three fobs, pushed the last one's button an extra 2 times to equal five since that is the minimum required.
5. Uttering thanks to the Jaguar gods that reside and lurk here on this forum, I then promptly collected my beloved...and drove 300 miles over the weekend, backroads, surface streets and intersate...to much rejoicing, excitement, and many sighs of relief...and 21 mpg (US gallons) average.

By the by, the odometer now indicates 150005 miles.
__________________________________________________ _______________________
Now if anyone has an idea for an SLCM electronics repair shop option in UT or Idaho, maybe even California?

LESSONS LEARNED
Go to the Jaguar forum FIRST!
Basic multimeter skills are must have.
Basic understanding of electricity and circuit theory is a must.
Determine if both brake lights are out. Adjust troubleshooting to match the situation. Once determining its not a failed bulb (swap with the working bulb from the other side) check that connectors are clean/dry/tight.
Have the correct wiring diagrams matching your car. Look one year up or one year down. Jolene's a 2001 model year with probably 2000 model year wiring colors didn't match the diagrams in the Jag service manual on the CD ROM so I spent valuable time milling in confusion. M. Stojanovic recognized that fact from my laments, and then helped us all out with wire color chart and color abbreviations; as well as a diagram that matched the wire colors in my car.
Most of us would not have guessed that the brake light bulb elements are powered through the SLCM - use the forum. How the esteemed member knew about the circuit card and the chips too?! I can only wish I wish I had that experience and expertise. I'm very grateful.
Unless the car is/was abused/neglected there should be no breaks in the wires and the connectors all seem dry and tight. Don't presume its in the wiring; general convention is that its usually a bulb, connector or control circuit/switch.
I was close to complete mental breakdown a couple of times due to the frustration of blind troubleshooting through the bundles of wires. Walk away for a day or so and come back to it. I had that luxury since I have alternate transport available.
Be slow and methodical; write your results down to help track what you've done and perhaps to help you recognize what you may need to revisit. I went back to square one a few times to methodize the troubleshooting in an environment I haven't worked in since 1979.

 

If you had voltage on the pin marked on the pic below when the brake pedal is pressed (and no right stop light), then the only problem is that chip. You don't need any special "SLCM repair" shop as any electronics repair shop (computers, TV, radios etc.), or an electronics hobbyist can easily do it if you also provide a new chip.