I replaced both of the brake light bulbs (dual filament ones) with new ones from the Dealership. Also took both of the bulb holder units out and cleaned all the contacts both on the bulbs and on the connector side. Just cant seem to shake the bulb fail message when I push the brakes. It only happens briefly and if I let of the pedal and repush it goes away. It also seems to happen more frequently at night when the lights are on.

Any ideas of where to go next with this?

 

As you have ruled out the common causes, the Fail message is normally the first indication of a lower voltage in the battery.
It can be as simple as a battery not re-charging sufficient due to short trips, or its age.

If I trickle charge my battery, the message stays away for months, but I need to bring the battery up to my apartment to do so.
So if I work a lot on my car, and without a real long ride, the same happens to mine.

 

+1 for battery charge level.

 

Does the center brake light work every time? The one on the rear package shelf. Could also be feedback from another socket on either side. Clean ALL the sockets and check the multi wire connector pins for corrosion. The large connector that plugs into the circuit board. Also make sure all the bulbs are clear, if any are slightly dark, that will raise resistance in the taillight circuit. Make sure no bulb has a brass base, all must be silver base bulbs.

 

Ahh OK thanks for the battery advice. I removed my battery and was trying to find a date on it but couldn't. I measured the voltage at around 12.5V but I still threw it on the charger and will see if that helps, otherwise i'll replace it. Its my understanding the voltage needs to be above 12.60 or so ?

 

Yes the center light works, I couldn't find any gold bases for the lights. Since it only comes on when i hit the brakes I thought it would have to be a brake light? I'll try to find this large connector that the tail lights go to and see what it looks like thanks.

 

You have a failure in the Security Locking and Control Module. Couple of choices: after finding which light is failing, hot wire from the upper, center light (does not go through the SLCM); find a replacement SLCM on eBay (must match your current unit -- Google or search this forum). There are companies that will repair the SLCM, but will down the vehicle for a period. DO NOT follow RobertDIY's cross wire solution (it will burn out both lamps).

 

After a bit of research I strongly believe this is the most likely cause of my problem. I would guess if it was simply a low voltage issue other problems would be present as well. So I ordered three of these High side power switch ics and will be replacing them myself. I do SMD work a lot (side business of repairing apple products) so this will be easy for me.

I ordered these as they look to be a good replacement for the current failing power switchers:
https://www.mouser.com/ProductDetail...y5qtQKPw%3d%3d

 

Let us know how you make out with those replacements. I've been putting off mine for a while, I have one that I'm sure my initial trailer wiring screwed up. I've bypassed it, but of course I get "Check Rear Lights" on every brake pedal push. Wouldn't mind getting past that. (Though it does at least make it easy to see that my brake switch had failed and not been releasing since the message would stick)

 

There is a common wiring problem of the grounds inside the 2 main lower lamp assemblies on the X308 or the 2 seater X100 I can't recall which

Ask questions

 

LP w/ the holiday themed schematics, upping the bar I see lol.

 

I'm just working with what I got , and that's not alot

 

Thank you very much I think this was in fact my problem. I did charge the battery while I was waiting on my parts to arrive from digikey but it appears I wont need them as the light seems to be gone still after the charging.

If anyone needs their SLCM redone with these high power switches let me know. I have three of them and can even solder them in for you. Just ask that you pay the 15 dollars or so it cost me to buy them.

 

I had this same problem a couple of days ago, messed with the bulbs, sometimes they didn't work, then they would, then they wouldn't, I checked all all the connections, grounds, etc. cleaned everything, checked everything, was driving me crazy. I charged the battery, which took so long that I realized it must be due for replacement. I replaced the battery and no more problems.

 

I have owned my XJ8 for 20 years now and have had this problem numerous times. It has always been a battery issue. Fully charge the battery and it goes away.

 

I had this issue on my XJ8 even with a new battery and ground straps on and off for about 10,000 miles. The issue turned out to be the high mounted 3rd brake light. Cleaned all the contact points and five new bulbs, no issues for 20K.

 

Same symptom for me. I found SLCM lamp drivers (one side only) to be the issue on my 2003 XJR. A lot of caution on un-solder/solder almost 3 years ago - no problem since. I posted the detail somewhere in the forum. Let me know if you need more info.

Good luck.