Tail light mystery...
 

Greetings Jaguarians...
My XJ8 has begun a wonderful new scavenger hunt game with me. Here's what happened:

I had been noticing that sometimes when I touched the brakes when decelerating off the highway I would see the "Check Rear Lights" warning pop up. I did check the rear lights and everything worked fine. But the message would still come up on decelerating. Okay.

Then I had a tail light bulb burn out. I replaced it but then I noticed that my tail lights were not coming on when every other light was on (headlights, side markers, backup, rear fogs etc. All of the bulbs in the rear tail light housing work-I replaced them all in trying to solve this puzzle. So then I noticed that if I had my headlight switch in the auto mode when it got dark the headlights and side makers would turn on (and my brake lights work when I touch the brake pedal by the way) but the "Check Rear Lights" warning would come up and the tail lights would not be on.

Then I found that if I started the engine and touched the brake pedal while moving the switch from off to auto-the tail lights would come on.

SO here's what I did to try to fix this issue:

New bulbs
New Body Processor Module (well, new to me. It was used but it made no difference to the fixing the issue)
I replaced the brake pedal switch.


Now I have the "Check rear lights" warning come on after almost every time I touch the brake pedal. I have paranoia that my brake lights are not coming coming on (they are but still ...)

SO

Anyone have any ideas about why this is happening? The steering column stalk switch works all of the other lights just fine so I am not suspecting the stalk switch. The body processor doesn't seem to have any effect as far as solving this problem and the brake pedal switch made no difference when I replaced it. (BTW Rock Auto sent me a Cherry Jaguar marked brake pedal switch so that was cool. I had ordered the cheaper one)

Does this have anything to do with the trunk mounted security module (and if so...why...?)

I would appreciate any help anyone has with this issue.

Thanks,

Scott

If you have done above things, and are sure all bulbs are connecting to their contacts fine, then the very first thing you should check is the condition of the battery.

In my car (which I don't drive that often), it is the very first thing which comes up if the battery is not fully topped-up.

And fully topped-up basically means a >100km ride, or a hug with the battery tender for a day.

For info, my battery is ~2 yrs old, perfectly fine, no any start issues whatsoever, just the warning from time to time, which always go away after above treatment.

Brake lightswitch gets a ground through the ignition switch at pin 3 and may be good enough for the king relays but not for this sub systemhttps://cimg2.ibsrv.net/gimg/www.jag...d714163109.png
https://cimg1.ibsrv.net/gimg/www.jag...e8204732e2.jpg

The check rear lights is common to the XJ8 and XK8. They really needed a hardier ground wire. Disconnect and examine the plug to the light assembly. The ground is the last wire in the connector. You will normally find it heat damaged. Clean the blade side on the light assembly with a stiff brush. The other plug will have to pieces of metal with the ends bent into an Ell shape. Heat usually distorts them and the gap between the ground connection appears larger than the other connections. Clean and gently re-bend them to close the gap. You should be good again for a few years and will then have to do it again.

I just can't resist this one....


http://2.bp.blogspot.com/-Sk55rJ45iV...Everywhere.jpg

Ah no self control!!! Damn funny though.

I had a problem with my taillights not working. Turned out to be a broken wire in the turn signal stalk. Link to my thread below.

https://www.jaguarforums.com/forum/x...orking-193530/

Had the same problem: took a SLCM replacement. Lots of threads.

If you separate the tail lights into 2 sections it is more manageable to fix one being the brake light which is higher priority . Do you get both left and right brake lights fail then look at the red wire . If you only get one side then look at the lens grounds and the purple power wire .

Was it ever solved?
 

Nope. I have been living with the issue. I just touch the brake pedal and then turn the lights off and back on manually. They the warning goes away and I know the tail lights are on. Weird. I still get the check tail lights warning when I brake from time to time.

Lord Donnington
2001 Carnival Red XJ8