From the manual:



"
A Direction light
B Reversing light
C Fog light
D Tail light
E Stop and tail light

Note that 12V 21W/5W stop/tail bulbs are fitted in positions E and D but the stop light in position D is not used.
"

 

It's these funky little gremlins that used to drive me crazy on my '67 E-Type. I was hoping modern electrical practices might exorcise the demons but evidently not. One would also think that, after so many years of British car ownership, that I would have learned to leave well enough alone. But oh no, I'm not that smart. So I'm guilty of experimenting with a pair of led bulbs in place of the standard incandescent brake bulbs. The lights worked perfectly but the "check rear lights" alarm appeared on the dash. Oops, the CANBUS didn't like the low resistance of the LED bulbs so I put the standard bulbs back in. Cool....not. The alarm will not clear. The original two bulbs are back in and but the alarm won't go away. All other bulbs are fine with matching wattage. Nothing else was changed. Ugh! I disconnected the battery and even grounded the positive lead hoping to discharge any capacitors that might provide residual current for memory circuits. Nope, went for a short drive and the alarm re-appears along with the "no cruise control avail" icing on my pity party cake. Now I'm pissed at the car and myself for being so stupid by evoking the past "Prince of Darkness" demons. (You old MG, Triumph, Jag guys know exactly what I'm referring to.) A wonderfully competent GT car without a working cruise control because of two bulbs. I can't find wiring diagrams or a proper (or improper) service manual so I went to the dealer out of an even mix of frustration and desperation. The diagnoses is a faulty brake switch. With diagnosis and fix that'll be $400 please. Wait! Changing two bulbs for a few seconds caused the platinum plated brake switch to fail? Step on the pedal, the brake lights work fine. Their answer was "it's a coincidence". Sorry but I'm not buying it. I firmly believe in British gremlins from too many years experience but not unrelated coincidences. Can something as innocuous as a bulb failure (which is what an led bulb would look like) cause the brake switch to fail? That's just mind boggling as digital 1's & 0's bounce through my little head. Need some advice from a genuine "Gremlin Buster". (speaking of which, can you believe AMC actually named a car the "Gremlin"? Talk about evoking a curse....)

 

Had this happen on my 05 after installing Silver star bulbs. Found a blown fuse in the trunk fuse block.

 

Last Winter or a couple months ago here in Houston, I noticed on the way home at night that all the newer Cars had these really bright Tail Lights and when they hit the Brakes, they were blinding! I asked around and found out about LED Bulbs! Well, you guys with bright lights aren't going to get the best of me! So, I ordered 10 LED Bulbs for my Tail Lights and put them in...Turned on the Lights and immediately got the old "Check Rear Lights" warning! Then I hit the Blinkers and man they really took off.....Blink,Blink,Blink,Blink! so fast I couldn't keep up with them! I pulled them out and put the good old English Bulbs back in......Thankfully, I did no damage to the system! Then, I was reading about LED Bulbs on the internet and found a new type of LED Bulb that was suppose to have resistors or something and would work with our CANbus system.....You guessed it, I ordered a set and rushed out and put those in....I'm go'na show those old Boys what a Jaguar can do! Well, they didn't work either......So, I finally woke-up and old stupid put my old Bulbs back in......What you should learn from this is "Don't Do it as they will not work in our Jags....."

Billy Clyde in Houston

 

Hi JJJ . . . just to clear at least one of your unanswered issues that are still dangling throughout this thread . . .

Forget your concern about what you see as weird behavior on removing a ground connection near battery. Please remember that for switching efficiency and heat dissipation, all reasonably modern cars (Jags earlier than most) employ "ground switching" technology . . . baffling many who go armed with test probes looking for power, because if fault free and fuses good, you'll find it everywhere. I'll bet all my peanuts that the wire you removed that offed both lights and warning light, was the main ground connection for the SLM . . . thereby shutting down the whole sub-system.

Next, be very, very careful about those twin filament globes . . . there are those that have keying pins offset longitudinally and others that are offset both longitudinally and axially. Don't just trust part numbers . . . check sockets. I say this despite knowing my market & MY is not yours, but it is a known issue.

. . . Oh, and to others posting side issues, can we please focus on just the OP's issue until resolved. Don't want to sound snitchy, and by all means post a new thread, but this problem is already confusing enough.

Cheers,

Ken

 

You're correct Ken and point taken. It may be relative to a more common and frustrating issue but still off topic specific to JJJ's original post.

 

More than likely, the problem is the brake switch. There are many threads about this. There are a couple of options for the part (repair or replace), and a couple of options for the installation (on or off the bracket), but expect some pain if you DIY. Brake switches seem to fail pretty frequently.

Just trying to get you help here, but if you need more help, please open another thread...

 

Ok. Hello All.

Thanks to everyone! I need to say that.

Its been a while, but again, I haven't really felt pressured believing that I'd get this figured out. That hasnt happened, lol, and yes, now I feel pressure. Inspection is up on May 1st. But still.

Slowly but surely I've changed all rear lights and the light sockets I can. No change. CRL message still screaming at me.

I hesitate to solder, as someone rightly pointed out, it can be dangerous. The SLM looks fine. Lazily I have not tested resistors yet but dont know that I can while they are in the board. Also as cat_as_trophy pointed out I am still unclear what the ground post thing is about from the OP...

I will also see what I can do to check brake light switch. Thanks Fmertz!

p.s. if i didnt mention ---- tensioner job went super smooth,,, its gotten to where I have a process now! Can do it in like 3-4 hours. Thing IS I'm still getting the haunting "PENDING" P1396 code (without full CEL) and I'm going to have to open her back up this Monday and Tuesday... Inspection time, remeber. Open to suggestions in a PM if there are any...? Still, she RUNZ great!!!

FEELS like I'm

 

For the resistors, disconnect the module then with your multimeter on ohms put the leads either side of the resistor. Measure them all, they should read the same ohmic value.

 

Hello All. Its been a while.

The inspection date has come and gone. Still, no solution to this problem but I'm getting closer. Again, no urgency - but I want this solved. Pssst - I got a bogus sticker, lol... Also working to solve CEL for VVT, timing and P1396 code that I struggle with (front of engine torn down now for the 3rd time). Cannot retard timing it seems. I've had a oil coolant return line burst on highway 2 weeks ago which sucked. Also trying to figure out how to rewire the SRS passenger airbag that the prior owner butchered by cutting the wiring harness to the passenger seat... Then a few more things. Car still runs beautifully. Traveling, top down, is addictive. Yes it is..

My problem with the CRlights is somehow and somewhere related to 3 things, possibly 4, as far as I can tell... The Boot Latch and Stoneworker lights (little lights at base of trunk below boot lid), the reverse lights and the common ground - as many as 6 leads on a post in the trunk near battery. Then, because the SWorker light share a common fuse with the left taillights, perhaps those are involved as well? FUSES

Ill try to describe whats happening the best I can. If I remove the common ground post (which will shut off reverse lights and SWorker lights) the Check Rear Lights indicator goes off. Interestingly the SWorker lights remain on but MUCH dimmer (un-grounded). A short? --- If I unplug the SWorker lights main plug and reattach the ground to post, no CRlight message but the reverse lights wont work. If I take ground to SWorker lights (still unplugged)and hard ground to body, no CRlight message but no reverse lights. Then any mix and match of trying different combinations but no fix. More,,, I have not found a diagram that includes SWorker Lights. See Attached.

I'm at a loss with electrical. And my truth - as I work I tend to get more disorganized in my thinking about the problem, than less.

PS... In this process, I've shorted out the tail lights on the left hand (drivers) side and CANNOT get them back on. Have checked all normal checks - fuses etc. Nothing.

Open to any suggestions AND no where close to giving up...

 

Are the rear side markers still working?

 

Hi!!! Yes. Yes they are.

 

OK then you've either got a wiring/connection problem between the SLM and the rear lamp cluster, or with the short you may have fried one of the previously pristine resistors in your SLM. Surprised it didn't take the fuse out, though...

 

Hi michaelh...

Sorry for the stunted reply earlier. Was commuting when I got your message.

I thought it should have blown the fuse,,, BUT in checking the fuse what I found was that the PO had taken a piece of copper wire and wrapped it around both poles of the fuse and reinserted into the fuse slot, effectively nulling the function of the fuse. Could end up being a big deal. My temp fix is rigging them to the working tail lights on the passenger side which seems to work fine - and - during my troubleshooting for the CRL message on my dash, this rigging doesn't seem to trigger the CRL message when I detach the ground that off's the CLR message.

Im looking into replacing the micro-switch in the trunk latch. There is something going on with the stoneworker lights, the reverse lights and that ground that I have to figure out. The problem is there. I just wish I was better with electronics. That they are dim when they should off is puzzling. I simply dont know how to search out a short like that. I also think its possible that one of the other ground wires that share that ground post could have current coming in from a short in another system and is feeding into the boot (stoneworker) light circut? What a pain.

 

Jay, did you ever get the warning light sorted out?