You apparently do not care to heed my advice nor take me up on my offer to walk you through the diagnostic procedure for this module for some reason. I offer one last piece of advice. If you diagnose these cars by parts changing, just because someone else's problem was fixed by some part, it will cost you a fortune. The parts are not cheap and there are lots of them. Diagnose, then repair or replace!

 

Hi, Just found this thread. BOTH of the rear brake lights in my 2001 XJ8 have suddenly stopped working; the third brake light remains functional. The bulbs appear okay, changed out the fuse, tried swapping out the relay without effect. The wire bundle at the right side of the trunk hinge appears clean and intact. Would anyone be able to share with me exactly how do I identify if the SCLM module is the cause of the brake light failure. Many thanks.

 

Also checked voltage at brake light bulbs both open and with brake pedal depressed reading 0 volts. All other lights- directional, reverse and running lights are working.

 

I did remove and clean all contact points on SCLM where I noted that it was obviously replaced by the previous owner as it had a 2006 manufacture date with my car being a 2001. I also noted one of the connectors having a Ford logo on it. Still looking for any thoughts or advice please.

 

Failure of both circuits in the SCLM would be unusual, so I might guess something else. Do you have a key fob? If so, do the brake lights flash when you lock / unlock the car, or when you set off the intrusion alarm? The high brake light is fired from an independent circuit, so it coming on is of little value!. Do you get a dash fault for lamps when you press the brake pedal?
It sound slike you have a multimeter. Can you read and follow a schematic? If not, no worries, we can guide you through it! Have you checked all of the fuses in the trunk?

 

Hi Ross, thanks for your reply. I can probably work my way through schematics with a bit of assistance andbhave downloaded the electrical handbook from this great forum. I have checked every fuse in the trunk and behind both heelboards, visually they all appear intact. I do receive the check rear light message when I step on the brake. When using the fob to unlock the vehicle, only the signal lights flash. When I activate the alarm the signal lights and running lights flash but no brake lights.
Thanks,
Neal.

 

At the advise of forum member Jack, I removed and opened the DCLM Module but don't see anything that looks obviously burned out around the three chips.

 

I can somewhat agree with this poster however this chip is KNOWN to fail. Bad design around the chip? I don't really know but they DO fail. Unusual to have both fail at one time? Yes but how does he know they both failed at one time since he had someone else tell him he had NO brake lights?
Anyhow as the poster asked Do you have a message on the dash telling you there is a problem with your brake lights? The chip is used to sense either an open or shorted bulb circuit. I think Jag designers made the rest of the circuit too much on the threshold to determine what was meant to be determined (open or shorted bulb circuit). I would replace one of the chips and see. And NO it does not cost the bundle in parts this poster was saying. If you can't buy the chips for less than US $5 then I will send you one for free.

Actually I just saw your message about the brake light warning on the dash. I would say replace one of the chips and test with someone watching your brake lights when you press the brake pedal. I will bet you one will work (the chip you replaced) and the other will not be working.

 

Usually the chip will have some damage look to it and these don't appear to but then again the chip can fail in a non disastrous way also. I have seen that too. Chips look normal but are messed up internally and will no longer works as designed.

 

WTF....I just ordered the chips and a new soldering iron online. I went to pop the DCLM Module back in the trunk until items arrive and guess what? I cannot for the life of me open the trunk. Won't open with remote understandably since I have the module in my hand, but the dashboard unlock button AND the key itself fail to unlock the trunk. Also, contrary to other postings the car does start without the module in place. Any thoughts or advice before I pay hundreds to a locksmith?

 

Pardon the aforementioned coarse language, I was able to gain access to the trunk manually after liberal dosing with WD40 and some vigorous key exercises. Perhaps just a reminder for all to periodically manually check the functioning of their locks!

 

Jack:
Yep. You and I agree. I asked the two questions to verify that it was probably NOT the brake light signal to the SCLM module that was amiss, and to verify thatt he module probably has power. So, I would say chip replacement is a good next step. And you are exacty right that the chip itself does give the no current signal. I have not experienced open circuit failures, but rather shorted chip ones (twice on on car and once on another ), so I am not sure of the behavior of the low current (lamp failure) circuit in this case.

Whitey:
I don't know your soldering experience level, but this is a fairly trickey job for a beginner. Remember that the chip itself is soldeed to the board on th back side. Youwill need to get it hot pretty quick using the heat sink edge away from the pins and pry it up with just a little force. I generally use a small screwdriver to edge in between thchip heatsin and th eboard as the older melts.

My method (and other's will have their own, I am sure) is to solder wick or solder suck the solder off the lead. then begine wedging with the screwdriver or wooden toothpick as I heat the main heatsink. Remove the old chip, clean up the solder lands, then resolder. For the main heat sink, the tricjk is get it hot fast and get the chip off before the board absorbs a lot of heat and burn or delaminates.

And if you screw up, fleabay has modules for about $100.00

 

The brake light demon or gremlin has at least temporarily exorcized from my XJ8! I ordered the soldering iron, solder wick, and replacement module chips. While waiting for the order to arrive I downloaded the wiring diagrams and ran the wiring harness again paying particular attention to the areas at the trunk hinge -still without result. Perhaps someone could help me with the schematics, but to me the wiring diagrams seem to indicate that the right sided brake light gets output from the SCLM whereas the left sided brake light gets output from the Body Processor Module. I was searching for a common wire to the two brake lights and came up with the Orange/Green which runs from the brake light switch to the SLCM and the trunk fuse box - no obvious break or damage. Just prior to sitting down with the soldering iron, I decided to unplug the brake switch connector under the dash and clean it and reconnect. Suddenly all brake lights are working as before! I'll save the module chips and soldering iron for later use, maybe just as a talisman to wave about the offending part to scare it back into good working order.

 

Whitey:
I don't know what schematic you are looking at, but have a look at this one. Both lH and RH stop lamps are driven by the SCLM:

 

Sorry my bad, those are indeed the schematics I was referring to. I guess I need a better magnifying glass. Although I still see both stop lamps appear to receive output from both the Body Processing Module and the SLCM with the RW and RB wires from the BPM. I feel fortunate that through sheer dumb luck I double checked the connection on the brake switch itself and thought it appropriate to share in case anyone else was tackling similar issues.

 

Whitey:
No sweat, but the wires you are referring to go to the "tail" lamp which is also sometimes called "running lights". The brake lights are connected to the SCLM because they are the brightest lights back there and they flash for Security functions.

 

Damm, now I see it. Definitely getting that magnifying glass. Thanks Sparkenzap.