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Suspension & Braking Forum by BimmerWorld
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Old 05-11-2016, 06:23 PM   #1
enzeno
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Join Date: May 2016
Location: Chesapeake, VA
Posts: 3
My Ride: 2002 325 xit Wagon
Another Brake Light Sticking On After Braking Issue - but with a catch

So I have been looking at many of the threads related to the brake lights staying on after braking, and I don't seem to come across any concrete fix, at least not that I can find. It is mixed in with the brake light failure indicators on the dash, among others. To be clear - my issue is related to braking, and the brake lights staying on after the brake is released. There is nothing wrong on the dash and the brakes work fine.

I have already replaced the brake light switch at the brake pedal. Did nothing. I have checked the bulbs, all look ok, and have been reseated. There is no char/burns on the wiring others have stated.

Now the catch - when the brake lights are stuck on - I can get them to turn off by doing almost anything electrical in the car. Meaning, that as long as a load is drawn and reduces voltage the brake lights turn off.

Example: Stopped at a light. Time to go, accelerate, brake lights stay on. I turn the headlights switch to on, and the brake lights go off. They stay off until I brake again, so there is no feedback or anything from the brake light switch at the pedal.

And its not just the headlights. Anything with a large draw. Even using the clutch to bog down the engine enough to reduce energy from the alternator will cause the brake lights to go off after being stuck on from braking.

Items I have tested that turn the brake lights off after being stuck on: Electric Windows, Electric Locks, Headlights, Fog Lights, Heated seats. Anything that draws something significant will cause the brake lights to turn off after being stuck on.

So in the end, it obviously seems to still be an electrical issue, but I am not sure where to go from here. I plan on inspecting the rear lights more, and double checking the ground wires, but they all looked fine today.

I am just hoping that someone may have some insight to the issue and to also know that there is an annoying little work around that you can use to turn them off if they are stuck on (providing that you have some way of knowing your brake lights are stuck on like my jury rigged mirror system that I am using to troubleshoot this issue).

TL;DR: Brake Lights Stuck On after braking, Switch at pedal replaced didnt help, wires look ok, electrical loads turn stuck on brake lights off.

Last edited by enzeno; 05-11-2016 at 06:24 PM.
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Old 05-12-2016, 07:58 AM   #2
markusmarkus
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Join Date: Jul 2008
Location: USA
Posts: 4,244
My Ride: 2001 330Ci
It sounds like a problem with the lighting control module (LKM). The LKM is the unit in the left side of the dash that has the headlight and fog light switches.
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Old 05-12-2016, 09:37 AM   #3
enzeno
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Join Date: May 2016
Location: Chesapeake, VA
Posts: 3
My Ride: 2002 325 xit Wagon
Thanks. I will check that out as a possibility and it seems very easy to get to. I did try further grounding the lights as a test, and it did nothing. Bulbs and everything are old, but work. Whatever the issue is, it is directly related to "too much" voltage being detected to turn the lights back off. The issue does not occur at all if the ignition is on with the engine off (~12 volts). If the car is running (~14 volts) the problem starts. And even more silly, if I turn everything on in the car, lights, fog lights, radio and HVAC fan on high, the brake lights will turn off when the car is at idle. It will not do that unless there is a large electrical draw. Continuing to troubleshoot...
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Old 05-13-2016, 08:49 AM   #4
enzeno
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Join Date: May 2016
Location: Chesapeake, VA
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My Ride: 2002 325 xit Wagon
So the brake lights are working correctly again. I removed the replacement brake light switch and returned the original one that was in the car and the problem went away (someone else had been through this as well). I can only assume that maybe the bulbs were not making a great connection and re-seating them made the issue go away, as I had already removed and reinstalled the original OEM brake switch to let it auto adjust before the replacement switch was installed - and the issue remained. I had checked the bulbs after the replacement non-oem switch was in place. Oh and one thing I did not mention in the original post was that the first thing I tried was replacing the #9 fuse and did not help (it was not blown, but it was corroded and loose).

So, I don't get the warm fuzzies about this fix at all about being permanent - but at least the are operating normally. And I will only buy OEM switches from now on - as this thing was a big ole pain and is getting returned.
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