E38: Bad Light Control Module? Low Beam Failure + Check Side Lights

[Formula E]

I recently revived my 1999 740i sport. Reason it went under the knife originally was an internal OSV failure. I ended up bypassing it for catch can/return system..a year later lol. Just put everything back together and charged the battery which ended up being completely shot. Obviously with that long of a dormant period.. I knew there would probably be a couple of surprises. Skimped out and gotta a deal on reconditioned battery, which fired the car up right away.

Now check computer reads out: Check Side Lights, Low Beam Failure, Check Fog Lights, Check Brake lights, Check coolant. All the side and turn signals lights work. There are actually a few break lights out and my fogs are disconnected so those make sense, along w/ coolant still bleeding.

Started driving it around, needed new gas and immediately notice driver xenon low beam starts to flicker and come back on, until it goes off completely and I cycle the switch to get it to come back. There is NO flickering inside the cabin or on dash lights when the headlight flickers. If you stand in front of the car.. one of headlights is running much brighter when they are both working.

From what I researched it seems like this could very well be LCM or related fuses. Checked/adjusted the battery connections, which I thought improved symptoms but not much, and probably just in my head. I can’t recall any these symptoms before the car went down/under knife over a year ago. Now the $100 I saved getting a reconditioned battery seems like it may have been a bad idea…because I can’t help but think it might all be voltage issue with the battery.

I was hoping to find similar issues with e38s out there but mostly found related symptoms in x5s, e39s.. all which run same module. Maybe one of you have come across this issue.. Please reply if you have advice or knowledge on this matter!

Thanks guys.

Quick video of low beam failing.

[Mayorchuck]

I think you're on the right track. My money is on the battery. This car is so picky on voltage. Unless you any reason to think water has found it's way to the LCM.

[kouks]

If the LCM fails you will lose turn signals and high beam. The low beam may come on intermittently on their own regardless of the light switch position. It may be going out and certain functions are not working. There are three different transistors in it and any one going bad could cause similar issues.

I'd replace all the bad bulbs you have first, then inspect all the rear tail light wiring in the trunk, maybe water damage or critter damage?

If the battery was really bad you'd also have other issues like transmission faults or speed sensors maybe, but it's possible that may be it.

[Formula E]

I think you're on the right track. My money is on the battery. This car is so picky on voltage. Unless you any reason to think water has found it's way to the LCM.

Yeah thats the pickle I found myself in. I need to find another working battery/e38/9 around that I can swap batteries really quick with to eliminate this theory. The car was garaged for most part and don't think the lcm would of got wet. My voltage read out is around 13.2-7 with the reconditioned battery installed.

If the LCM fails you will lose turn signals and high beam. The low beam may come on intermittently on their own regardless of the light switch position. It may be going out and certain functions are not working. There are three different transistors in it and any one going bad could cause similar issues.

I'd replace all the bad bulbs you have first, then inspect all the rear tail light wiring in the trunk, maybe water damage or critter damage?

If the battery was really bad you'd also have other issues like transmission faults or speed sensors maybe, but it's possible that may be it.

All LCM stories I researched with e38s dont match directly with my symptoms. Like high beams, loss of turn signals, low beam on without key.. none of those have happened. I get check side lights but they still work. I've double check tons of wires, nothing spotted. Critter damage unlikely but possible I guess? It sat outside for 3 months before being parked in garage for year.

[Formula E]

Update: Found another lcmIII from local board member and replaced mine with it...Received the exact same symptoms still. Also no cluster warning to reprogram it either, which I thought would be the case. Went ahead and put back the original LCM, since this didn't remedy the issue. Now I had enough , Ill buy a new battery... Had to rule out scenario. This didn't work either.. same symptoms.

Im now back to square one. Possibly thinking its a ground issue of some sort. Any more advice would be greatly appreciated!


Cliff notes on issue:
Turn on car receive: check sidelights, check brake lights, Check fog lights, check coolant and low beams fire up, flicker until driver side dies. Passenger remains light. Driver side Corner light flickers off and on as well. Check Low beam warning comes on after eventual failure(usually 30 seconds or when another accessory is turned on such as ac or door opening. I have my fogs disconnected and wiring for these have received some damage. Car is super low and front bumper has taken a beating. Possibly related?

[Mayorchuck]

You would not get a warning to code the LCM. You may get a tamper dot next to the mileage but all that means is the IKE (cluster) and LCM do not have matching VIN's and are not communicating for mileage and such. So I don't think, if it were mine, that I would rule out the LCM just yet. You may also have some I-Bus issues. You really need more powerful software to diagnose the issue at this point. Any good German independent shop should have BMW software to scan the car. Many members here do as well but not sure if any are close to you.

One other thought is the fuse block under the passenger seat. The LCM is fed by one of them directly. It sits in the lowest point under the passenger seat. It's a common collection point for water from leaking sunroof drains.

[Formula E]

You would not get a warning to code the LCM. You may get a tamper dot next to the mileage but all that means is the IKE (cluster) and LCM do not have matching VIN's and are not communicating for mileage and such. So I don't think, if it were mine, that I would rule out the LCM just yet. You may also have some I-Bus issues. You really need more powerful software to diagnose the issue at this point. Any good German independent shop should have BMW software to scan the car. Many members here do as well but not sure if any are close to you.

One other thought is the fuse block under the passenger seat. The LCM is fed by one of them directly. It sits in the lowest point under the passenger seat. It's a common collection point for water from leaking sunroof drains.

Checked these fuses, all them tested out and looked immaculate. Was nice to clean the carpet at least haha. Decided to replace the corner light which stopped if from failing/flickering along side the headlight. Go figure.. Now i'm down just to the driver side low beam. All other check signals, brake lights(3rd burnt holder) fixed as well. Decided it may just be the ballast to the drive side. Ordered a replacement d2s for a decent price so we shall see. These symptoms combined, and battery failure at same time didn't help but yep should of done this first lol!

Good news is the other battery I purchased should barely squeeze in my E36 M3 which needs a replacement.

[jre302]

I have the same problem. Any solutions......

[Chamberlin]

Any chance for a bad headlight switch? I just rebuilt my headlights today using some spare xenon assemblies I got off eBay. I re-used my ballasts, bulbs, and front glass, but replaced the housings with the nicer eBay units. The turn signals are brand new OEM, but I'm re-using the original turn signal sockets, as the new housings came with just single filament sockets and bulbs.

My symptoms are different than the OP's, in that my front turn signals work, and my parking lights work (using dual filament bulbs of course), but when I turn on the headlights, the right side parking light goes out. Comes back on when the headlights are turned off. Could it be a faulty headlight switch? I will check the rear parking lights tomorrow as that might help support that theory. Just wanted to see if anyone heard of a faulty headlight switch in these cars before.

Update: the rear right side parking light stays on regardless of headlights being on or not... Hazards/turn signals work normally, again regardless of the headlights. It's just the front right parking light filament that goes out when the headlights are on!

[ripley76er]

my dashlights and all backlit switches are out also my exterior lights wont work unless car is on, no longer have alerts; “lights on” or “check tail light” that used to come on either. All digital lights do work tho.
would this be LCM?
I replaced ignition, dimmer & headlight switches with no results.
Any help?

[Philip43]

I recently revived my 1999 740i sport. Reason it went under the knife originally was an internal OSV failure. I ended up bypassing it for catch can/return system..a year later lol. Just put everything back together and charged the battery which ended up being completely shot. Obviously with that long of a dormant period.. I knew there would probably be a couple of surprises. Skimped out and gotta a deal on reconditioned battery, which fired the car up right away.

Now check computer reads out: Check Side Lights, Low Beam Failure, Check Fog Lights, Check Brake lights, Check coolant. All the side and turn signals lights work. There are actually a few break lights out and my fogs are disconnected so those make sense, along w/ coolant still bleeding.

Started driving it around, needed new gas and immediately notice driver xenon low beam starts to flicker and come back on, until it goes off completely and I cycle the switch to get it to come back. There is NO flickering inside the cabin or on dash lights when the headlight flickers. If you stand in front of the car.. one of headlights is running much brighter when they are both working.

From what I researched it seems like this could very well be LCM or related fuses. Checked/adjusted the battery connections, which I thought improved symptoms but not much, and probably just in my head. I can’t recall any these symptoms before the car went down/under knife over a year ago. Now the $100 I saved getting a reconditioned battery seems like it may have been a bad idea…because I can’t help but think it might all be voltage issue with the battery.

I was hoping to find similar issues with e38s out there but mostly found related symptoms in x5s, e39s.. all which run same module. Maybe one of you have come across this issue.. Please reply if you have advice or knowledge on this matter!

Thanks guys.

Quick video of low beam failing.

This is an old thread I know, but just thought I'd give my tuppence worth.
Your 'Check **** lights' message is coming on because the LCM works on resistance, and not voltage. In other words, as bulbs become worn through use, their resistance reduces, and the LCM thinks the bulb is blown, when it's not.
Ask me how I know!!