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Rob S

LKM questions-The truth is out there....

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Hello my learned 5 lovers :D

As some of you may have read, my beloved car has a curious electrical glitch which only shows itself when I have the lights on. The dash CCM starts showing a list of faults (which thankfully don't exist) such as licence plate light, dip beam, tail light etc etc (so faults at front and rear). I've been advised on here it's the LKM.

Now I want a definitive answer, does a replacement used module require re-coding?

Does it affect my cars odometer speedo reading?

Or is the new unit just a plug and play glorified fuse? I look forward to the truth, as Jimmy is kindly holding one for me!

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Hi Rob.

All lights work perfectly. The most annoying thing is that it over-rides the diplay for temp/ clock ect. Oh and the annoying chime! :roll:

That's definitely the CCM, LKM stops the lights from working. You can turn the gong off but I can't remember which OBC button does it, got a feeling it's the S/R button.

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Thanks for the info e28m5. where's the ccm located and is it easy to swap?

cheers

nick

It's in the fusebox, second largest module next to the LKM.

Earlier ones were metal with a black plastic top, later ones were all black plastic.

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Now I m really confused. So if the LKM is knackered it will stop the lights working? I thought from other threads it could be responsible for false messages to be displayed.

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Now I m really confused. So if the LKM is knackered it will stop the lights working? I thought from other threads it could be responsible for false messages to be displayed.

LKM - Light Control Module, literally controls the lights via various relays, circuits etc. Common fault on E34s for this to pack up and switch your lights off and on intermittently or only let you use sidelights and no main beam etc.

CCM - Check Control Module, responsible for displaying messages on your dash via a series of sensors. Washer bottles, low water, low oil etc. If this packs up it will display warning messages when there's obviously nothing wrong.

There was a recall for 95 and 96 E34s to have headlight beam throw adjusters changed which allegedly cured the fault but didn't :roll:

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So not wishing to be dense, but if my CCM is giving messages about lighting faults, and then lights are all working ok, then its the CCM thats at fault, and not the LKM?

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So not wishing to be dense, but if my CCM is giving messages about lighting faults, and then lights are all working ok, then its the CCM thats at fault, and not the LKM?

Usually although sometimes bad earths in the rear lights can fool the CCM into thinking they're not working.

Before you fork out for a new CCM, clean all the bulbs and bulb holders and check the wiring loom that runs into your boot-lid for any obvious damage, especially where it's attached to the left hand "hinge"

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Ta. mines all black plastic , noticed it when swapping the LKM. Just need to locate a CCM now. Thanks for the info 8)

I have one here you can have for free mate :wink:

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Update:

A very kind soul loaned me a LKM to try, and it s not made any difference :cry:

So next stop, whip out all the bulbs etc. But i reckon its the CCM as per E28M5's post.

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Just to add to this a little some time ago I read somewhere online that the problem with the LKM is generaly dry/cracked joints in the solder. The piece had pics circling the usual spots. Cant seem to find it now, however some years back I had the issue with my dipped beam randomly switching on and off. I pulled the black cover off the unit to reveal the pcb underneath and sure enough you coud see the cracked solder 5 mins and a soldering iron, problem fixed. I will keep looking if I can find it again I will post the link.

http://www.e32fixes.com/results.asp?met ... ix&fixid=2

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I'm just resurrecting this thread as I have this exact same problem on my '95 E34 540i.

 

HOWEVER  after doing all the usual bulb, contact checks etc. and checking inside the LKM that there aren't any broken solders (it looks different inside mine to the one I've seen where the guy recommends re-soldering the connections to the relays inside...almost as if by then BMW had upgraded the solders to a much thicker type) I've narrowed it down to this:

 

If I disconnect the headlamp height adjuster motors this problem goes away i.e. no spurious light warning messages. If I connect one of them back up again the problem occurs straightaway. And it doesn't matter which one I reconnect, left or right, it happens immediately.

 

I read somewhere on this forum that someone was talking about a faulty capacitor inside the headlamp adjuster motors? They were going to pull the adjuster motors and replace the capacitors? But then I think the thread fizzled out.

 

Any ideas/ thoughts?

 

Many thanks in advance.

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I've done a bit more research on this topic and found this on bimmerforums.com and there seems to be a more definitive solution to this problem:

 

attack eagle
08-23-2010, 11:10 AM
yep, the rf feedback from failing motors will induce false errors. Well known issue.
A capacitor could help as a filter.

But I can tell you one permanent fix...

Get them off the LKM. They run thru the LKM factory, though they do not NEED to.

Wire them directly from the switch without traveling thru the LKM or connecting to it for power... I retrofitted them into my e34 a few years ago, used the stereo power as power for the circuit. Never got an error, and they were Old and Cruddy motors.
 
Now I just need to ask..."How do I do this?"
 
Or should I just leave it to my mechanic as I'm no electronics expert...in fact I have no electronics knowledge at all!
 
Thanks
 
 

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my solution was to buy new head light level adjusting motors direct from shop.bmwclassic.com with the associated holders

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Derin, have you tested your motors yet?  With the engine off, the fan off, and the ignition at position 2, try adjusting the beam of the lights by pushing the beam adjustment wheel from 0 to 2.  You should hear two motors whirling.  If you do, they are working, if you don't obviously they are broken.

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Thanks guys.

 

I haven't done exactly as you described above but I have had the lights shining against something, moved the adjustment wheel and can see the height of the beam change so assumed they are working?

 

The issue doesn't seem to be that the headlamps themselves don't adjust but rather that when they are connected I get all the spurious warnings of various lights being out (brake light, tail light, licence light) come up on the dash display when in fact they are working fine. If I then disconnect the headlamp adjuster motors, I don't get these warnings.

 

Steven, how much were the holders when you bought them? And was it a pain of a job to swap the new ones in?

 

Thanks again.

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