I Need Some Help with a Weird/Confusing Problem with X5 Xenon Headlights
 

I have a 2006 X5 3.0i with about 133K miles. I noticed that the driver side Xenon light wasn't working. I bought a new $100 bulb, but it didn't help. So I have decided to dig deeper but am now totally confused and frustrated.

I have a lot of experience troubleshooting and repairing BMWs, but have never run into something so illogical. I've spent several hours trying to figure this out, and I'll give an overview of everything I've tried so far.

I replaced the bulb and it didn't help, so I swapped the xenon igniters side to side - that didn't make any difference. So now I got serious. I removed the front bumper and actually swapped the entire lights side to side. Again, only the one on the passenger side worked. So it's most likely not a problem with the lights themselves.

I discovered that if I move the headlight switch between the normal on position and automatic and toggle the high beams and flash-to-pass, sometimes the driver side light will come on, but then the passenger side goes out. If I toggle and flash some more, I can get both lights working. Once they both begin to work, they will stay on.

Additionally, there are no warnings or messages in the Check Control. Although it will occasionally display a message about the low beam lights at the same time that the passenger side switches on and the driver side switches off.

If I shut the car off, I have to start all over again because the driver side light once again won’t turn on.

I have access to another X5, so I tried swapping the headlight switch to see if that was the problem. It made no difference.

Using DIS, if I enter the Activation mode, I can individually control the lights regardless of the headlight switch position. Using this test mode, I can turn on each headlight individually. Doing that, they each work every time. I can turn them on and off as much as I want and they work every time - but I can only test them one at a time. I don’t have a way to activate both lights simultaneously using DIS.

When I check the error memory, there is only one error. If I clear the error and check again, it comes right back. This is the error:

LCM Light/Check Module IV
3E LCM: Fault, ALC control unit

Based on this troubleshooting, and the nature of the error, I’m inclined to think the problem is with the light control module. But they are expensive and I don’t want to just throw one at it to see what happens. Are there any other tests I can perform to make sure the problem is the LCM?

Could the problem be something else entirely, but I’m just not seeing it because I’m focused on the LCM?

I had a similar issue, but not the same issue on an e83. If the lights were on automatic, the right blinker wouldnt work when I put the stalk to indicate right. If I put the stalk to indicate left, the right blinker would then work. The problem ended up being the switch, not the LCM. I know its not the same issue, but it could be the same problem, if not then just something to consider.

Shoot I just read this twice and I'm stumped.

Wait a second. I think I know. Do you have the stupid Adaptive Lights on the 2006?

ALC Control Unit sounds to me like (Adaptive Lighting Contol is my interpretation of the abbreviation) its a fault in the Adaptive Lighting system, perhaps that fault is what is keeping the lights from being triggered properly. Unfortunately I don't know where the ALC module is, is it under the light?

I think it does have adaptive lights. There is a module under each light, but the individual lights are working fine.

Replace that module and you should have your problem fixed then. Or perhaps its a nicked wire or bad connection, check it out. Its definitely related to Adaptive function though from what I'm reading.

I'd say swap the LCM from the other X5 but that may require coding. It sounds like your LCM took a dump which they occasionally do (especially with the help of moisture). I can't see the adaptive system giving you this issue.

Let me bounce this off you:

When I hook it up to DIS, I can activate each of the lights in the car individually (left low beam, right high beam, left fog light, right brake light, etc). When I perform that test, the lights work perfectly every time. The problem also doesn't change if I swap the entire lights side to side.

If the problem is with the module in the light itself (or the bulb or the igniter), the light wouldn't work during the test, correct? But it does. So that makes me think the problem is not with the actual headlight.

Plus there's this: 3E LCM: Fault, ALC control unit

I don't think there is anything wrong with the headlight on either side. I think there is some sort of short inside of the Light Control Module (LCM). The LCM and the ALC control unit are two individual modules however there is a portion of the LCM that interacts with the ALC module. Using my often flawed logic if it's giving you fault codes for LCM: ALC I would assume its an issue with the actual LCM. Had it given you a fault code for JUST the ALC module it would be a different story but again I don't think that would actually prevent anything from working.I believe the unit itself is faulty.

I am not very familiar with how DIS, GT1, auto logic, or how any really work with checking modules so I can't touch on that but it definitely seems like an LCM issue from my previous experience's with my 01 740i.

Search SiteSearch 61356961140 - 61356961140 - MODULE - ES#169173

RealOEM.com - Online BMW Parts Catalog

Again I'm not sure but because the fault seems to come off the LCM specifically I would start there. Maybe just try disconnecting and reconnecting it once to see if anything changes and/or check if there are any software updates for the actual LCM?

http://www.xoutpost.com/bmw-sav-foru...ease-help.html

According to this thread the ALC module is behind the glovebox as well. Under the headlight is a separate module.

Ricky Bobby:

Yes, I unplugged the entire light assembly and swapped them side to side. I did swap just the bulbs and igniters at first, but, well, the situation escalated…

From what I can tell, there are at least 5 modules to control the lights. Good to know about the ALC module location. I was thinking that's where it would be, but it's good to have confirmation.

How many modules does it take to change a light bulb on a BMW?