Hi,

I posted this as a reply to this thread but got no reply, can anyone on this forum help?

I have this problem of intermittent right hand side brake light failure on my UK 2005 XKR convertible.

I have located the SLCM and it's part number is LJA1970AC/ XXXX as reported in post number 58.

I've removed the bulb holder & cleaned all the contacts but the warning "check rear lights" is still occurring.

I have removed the spare wheel and had a good look around, under carpet etc, but cannot find the VCATS sticker, anyone and idea why, maybe it was relocated in later cars??

Is there another solution to replacing the SLCM, does anyone repair them?

Thanks for your assistance

 

Hi John,
First check that you have a voltage on BT31 pin 2 at the tail light, that is the blue wire.

If you don't, disconnect BT42 from the SLCM and check the continuity along the blue line to the tail light.

If that is ok then your problem will most likely be the resistor for the sensing line in the module, and that can be repaired.

Hope this helps,

 

Hi.

These cars have a history of failed or melted ground connection from the tail light Assembly.

 

+1 on checking the ground connection - there are a few posts in the forum with a quick and easy fix.

 

I get the same symptoms priop to a bulb failure. Now I just change the bulb at the first signs at that cures it.

 

+1 on change the bulb. When you get the warning is the light working? I have plled the bulb out of the socket and it would start working again for a day or two. Then the problem would return, changed the bulb problem solved. Jim

 

another possibility (happened with my 03) try to use the cruise control when it happens next, if 'cruise not available', then its your brake pedal switch...and a reasonable DIY project

 

Thanks for all your replies.

I've changed the brake light bulb to no effect & also noted that I also get the warning message come on when driving with the lights on without having touched the brake pedal so I don't think it's the brake pedal switch especially as it's only the driver's side that's not lit.

I've checked the rear light assembly and the contacts are not scorched as in this post so I don't think there's any point in adding an extra earth wire to it.

So it's looking more & more like it's the SLCM. Anyone know why I can't find the VCATS sticker in the spare wheel well or where it's located?

Thanks again for you suggestions.

 

I had the exact same problem throughout the summer. Check rear light warning came on once a week, had to change bulbs twice. One of the Forum guys suggested drill a hole into the rear light assembly ,and run a wire to a convenient suitable ground on the body. There are a few empty holes from manufacturing the body,so I went to one 6-10 inches away and set it with a sheet metal screw. It took maybe ten minutes to do and another ten minutes for congratulating myself. No more problem,end of story. So, you need a piece of wire about 10inches long with an eye on each end, and a drill to make a hole, screwdriver, and two screws. It's a piece of pie...

 

Agreed, it's searching for a ground through any possible means. Many European cars have used the same type lamp cards for years and they've always been crap, no matter what manufacturer.

 

Thanks for your suggestions.

I've soldered a length of wire to the earth section of the circuit board & fixed the other end to one of the bolts holding the light housing to the body, tested everything still works & I'm happy.

I'm sceptical that'll it'll fix the problem as there's no scorching of the connectors on mine as there are in this picture posted by the guy who originally sugested this solution. If you look carefully you can see the scorch marks on the connectors.

I'll let you know how I get on.

Is there no one who can tell me where to find the VCATS sticker on my car?

Thanks again.

 

VCATS should be in the boot, under or aft of the spare.

 

I too am having this on my 01 XK8. I've noticed the LED at the rocker switch that arms the cruise control goes out when I get the warning message. I believe it is my brake light switch because ALL lights work normally.


An interesting side note..... My back-up sensor alarm (beep) stays on constantly in reverse while I'm getting the warning......any comments or experience with this?

 

Usually when weird stuff happens you've got a bad ground, the current is trying to find a ground by flowing through other devices until it finds one.

 

Checking the ground wire is the first thing to check but check both sides and clean them at the same time. As for the bulb contact you should remove all the bulbs and scrape clean all contact area and bulbs. Just yesterday I had the same problem and found that oxidation on the contact were my problem. I sanded lightly all the contacts and added dielectric paste and all is good.

 

I've now soldered earth wires to both the earth section of the circuit boards & fixed the other end to one of the bolts holding the light housing to the body. I've tested the earths, both directly on the circuit board & the light housing fixing bolts & they're fine. I've also removed all bulbs & cleaned the contact areas with an abrasive.

The "check rear lights" warning does still illuminate, even though all rear lights are working when it's illuminated.

With the warning message illuminated I tried H2OBOY's suggestion of activating the cruise control but none of the buttons produce any response, does anyone have any suggestions on why this could be or suggestions for investigations??

The Automatic Speed Limiter (ASL) works fine.

Thanks again for your help.

 

Sounds like you're back to the Brake light switch (aka, stop light switch) under the brake pedal with it's two micro switches, one of which deactivates cruise control (and the other activates brake lights). All IMHO !

 

Thanks for that, I'll get it checked out.

So does mine.

 

Finally got around to fixing this by replacing the brake pedal position switch as previously recommended, nothing wrong with the security locking module.

Thanks for your help.