Fix for infamous LBF problem

[dRock13]

thank you! is there a way to wire it so we don't need to just cut the wires though? what do these LBF harnesses actually do?

[RRSperry]

The check control module monitors the current going to the light bulbs. If enough current isn't being drawn, it tells the OBC that the bulb is out. Since HID bulbs use about 1/3 less running current that incandescent (halogen) bulbs, it thinks the bulb is out.

You can put a resistor in parallel with the power supply to the ballast. (a little calculation now...) 55W=IxE so I = 55W/12.8V= 4.3A (for a normal 55W 9005 bulb)

A 35W Hid is 35W//12.8= 2.73A

So Seeing as how you have to drop 1.56A, and P= I^2R, Mix and match, and voila...

I^2R= IE... R=IE/I^2... 20W,8.2 Ohms resistor ...

Or just cut the damn wires...

[Brent 930]

^Inline sounds like series, it needs to be paralleled, but you have your formulas correct.

I was under the assumption the HID's might actually draw more current because after they're used the LBF circuit will no longer work. That is, the shunts get damaged....but if they draw less current what is actually getting damaged? Unless maybe there is some serious ripple that will damage them. After all they're paper thin shunts.

I just modified the box instead of cutting any wires.

[RRSperry]

You want it in parallel, to draw additional current. Having it in line would drop voltage... Sorry I was unclear. I edited the above post.

It has nothing to do with damaging the Check Control Module. HID's draw more current at startup, and less when running. It's the running current that triggers the LBF message. Anyway, I cut the wires, and installed Molex connectors if I ever want to go back to stock.

[Brent 930]

^Ahhh, so the current on start up does spike and therefor is why the shunts get damaged/out of calibration and thus they won't report correctly anymore.

I just did a few trace cuts to isolate the shunts from the circuit but still bypassing the current at the same time.

[RRSperry]

Nothing gets damaged, it's working as it is supposed to. If you put the stock lights back in, the LBF would go away.

[mmaigret]

The OBC could potentially be damaged by a current spike if one were to power the ballasts from the low beam circuit rather than a switched relay.

[Brent 930]

Nothing gets damaged, it's working as it is supposed to. If you put the stock lights back in, the LBF would go away.

That isn't true, at least in all cases, and none that I know of including myself.

[DeM3n]

Just did this "mod." Very nice. Worked like a charm. My LBF is now fixed! Thanks OP!

[EnderG60]

The check control module monitors the current going to the light bulbs. If enough current isn't being drawn, it tells the OBC that the bulb is out. Since HID bulbs use about 1/3 less running current that incandescent (halogen) bulbs, it thinks the bulb is out.

You can put a resistor in parallel with the power supply to the ballast. (a little calculation now...) 55W=IxE so I = 55W/12.8V= 4.3A (for a normal 55W 9005 bulb)

A 35W Hid is 35W//12.8= 2.73A

So Seeing as how you have to drop 1.56A, and P= I^2R, Mix and match, and voila...

I^2R= IE... R=IE/I^2... 20W,8.2 Ohms resistor ...

Or just cut the damn wires...

if this is true then why do I still get a LBF with my 55w HID's?

[goodlife]

Thank you very much!! Worked just like it was supposed to. I was very tempted to just rip out the OBC and toss it...Now just to fix the stupid brake circuit malfunction.

[Hova]

mod worked perfectly!!




thanks OP!!!

[ZoomZoom951]

EDIT wrong post.

[AT]

Absolutely one of the easiest and most benficial mods to your vehicle if you are using any HID lighting setups. This just took me 15 minutes from start to finish and it's working great.

I elected to NOT use any connectors and simply stripped the wires half an inch and wove the red/blue and green/gray wires into each other, then covered them in electrical tape and tucked them away. This way I will have an easier time returning the wiring back to factory form should I ever choose to sell the vehicle.

Thank you again to the OP'er, you're an awesome guy for figuring this out

[jps1995m3]

sound's good !!.....i have to give this a shot....

[BRAAP]

Car;
’97 M3 sedan, Cosmos black.
Bought the car little over a month ago, all lights are original except for the fogs, previous owner installed Depo fogs.

Ordered Smoked front markers and smoked side blinkers from Umnitza. Had such great success that I ordered the Umnitza Depo Euro Ellipsoids with Xenon 50w upgrade, (then also ordered smoked tails, should see those late next week…) Matt and Tim both have been very patient and making every effort to help me through some headlight woes! Thank you Tim and Matt for your patience and efforts in help “clearing up” these issues.

At any rate, installed the new lights, installed 15 amp fuses and right away, LBF in the OBC. Removed the Euro lights and reinstalled my original headlights and still have the LBF indication. Thank you to Matt at Umnitza for steering in me in the direction of this thread.

Using this concept for removing the CCM from the low beam circuit fixed my LBF indication in the OBC, (this mod still allows the CCM to monitor the rest of the lighting system just fine…) Personally I do not understand why BMW implemented the headlight failure detection system to begin with?! For the rest of the exterior lights it makes sense, but NOT for the headlights!? If this next statement offends anyone, please accept my apologies as I have no intentions of offending anyone, only playing captain obvious.

Personally I feel that if any driver of any motor vehicle is so inattentive when behind the wheel of a motor vehicle that they “require” an illuminated dash indication to tell them that one or both of their head lights is inoperative, they shouldn’t be allowed to drive a motor vehicle! Honestly!? If you have your head lights on, it is because you need them to “see” with. If they don’t work, you aren’t going to be able to see as well. With “vision” being a prerequisite to driving a car, if you can’t distinguish from being able to see and not, then it’s time to hand over your keys and surrender your license! Of course this is just my not so humble opinion.


Next project, that pretty little red Airbag light that just decided it was time to illuminate yesterday! DOH!


Paul Ruschman
Rusch Motorsports

[pedro05]

I have had LBF with HIDS... removed them and the fault is still there... any clues?

[BRAAP]

I had the same issue an didn't much really care because I was going to perform the LBF fix for the following reason...

Personally I feel that if any driver of any motor vehicle is so inattentive when behind the wheel of a motor vehicle that they “require” an illuminated dash indication to tell them that one or both of their head lights is inoperative, they shouldn’t be allowed to drive a motor vehicle! Honestly!? If you have your head lights on, it is because you need them to “see” with. If they don’t work, you aren’t going to be able to see as well. With “vision” being a prerequisite to driving a car, if you can’t distinguish from being able to see and not, then it’s time to hand over your keys and surrender your license! Of course this is just my not so humble opinion.

... I then performed the LBF mod, now I get NO more LBF warnings and the computer is still able to monitor the rest of the lights in the car just as it always has.

[clumpymold]

Car;
Personally I feel that if any driver of any motor vehicle is so inattentive when behind the wheel of a motor vehicle that they “require” an illuminated dash indication to tell them that one or both of their head lights is inoperative, they shouldn’t be allowed to drive a motor vehicle! Honestly!? If you have your head lights on, it is because you need them to “see” with. If they don’t work, you aren’t going to be able to see as well. With “vision” being a prerequisite to driving a car, if you can’t distinguish from being able to see and not, then it’s time to hand over your keys and surrender your license! Of course this is just my not so humble opinion.


Next project, that pretty little red Airbag light that just decided it was time to illuminate yesterday! DOH!


Paul Ruschman
Rusch Motorsports

Haha, that sounds funny. But you'd be surprised as to how bright some HIDs are and it's not THAT easy to tell if one of them is out. Especially around more well lit areas.

[LockDots]

Just did this yesterday and it worked like a charm.

Thank you OP!

[BMWMPow3r]

nice write-up

[bmwpowere36m3]

nice-writeup

[rwle36]

I did this a couple weeks ago, and no more LBF. But today on my way to school, my ASC light and my ABS light came on at the same time just driving down the highway. After I turned my car off they went away... could that be related to me cutting those wires?

[Brent 930]

^Nope

You guys didn't need to cut your wires to get rid of the LBF as I stated earlier.

[RRSperry]

Post hoc ergo propter hoc...