Rear Brake Lights Won't Turn OFF

[danewilson77]

Posting for a friend. Any help/Idea's is/are greatly appreciated.

His quote:

"Still battling the gremlins. Changed alternator Saturday and installed a new AGM battery today. Car was fine leaving the battery shop. Came home opened and closed the windows with the car off and then started it. Damn brake lights light up and radio off. I'm about ready to drive it to a rough neighborhood and leave the keys in it."

"I replaced the fuses mentioned. Did the tail light ground. Replaced alternator and battery. The problem is intermittent but only happens when starting the car. It clears up after a few minutes sometimes and sometimes doesn't. Radio doesn't work when fault is present. That is what lead me to battery and alternator. My Mercedes shuts down non critical systems when voltage is low. Could the ignition switch be the problem. Also the passenger door lock actuator does not operate with key fob but usually does with button on console. I have checked all fuses in glove box and relays and fuses under the hood. Are there others I am missing. When this first started we replaced the brake pedal switch."

[mbeckel]

Posting for a friend. Any help/Idea's is/are greatly appreciated.

His quote:

"Still battling the gremlins. Changed alternator Saturday and installed a new AGM battery today. Car was fine leaving the battery shop. Came home opened and closed the windows with the car off and then started it. Damn brake lights light up and radio off. I'm about ready to drive it to a rough neighborhood and leave the keys in it."

"I replaced the fuses mentioned. Did the tail light ground. Replaced alternator and battery. The problem is intermittent but only happens when starting the car. It clears up after a few minutes sometimes and sometimes doesn't. Radio doesn't work when fault is present. That is what lead me to battery and alternator. My Mercedes shuts down non critical systems when voltage is low. Could the ignition switch be the problem. Also the passenger door lock actuator does not operate with key fob but usually does with button on console. I have checked all fuses in glove box and relays and fuses under the hood. Are there others I am missing. When this first started we replaced the brake pedal switch."

Did this individual get the recall work done on the tail lights? I know a few years ago that bmw had a recall on the e46 taillight assemblies

Sent from in the bushes

[danewilson77]

Yes. Tail light recall has been performed. More info below:

"I replaced the fuses mentioned. Did the tail light ground. Replaced alternator and battery. The problem is intermittent but only happens when starting the car. It clears up after a few minutes sometimes and sometimes doesn't. Radio doesn't work when fault is present. That is what lead me to battery and alternator. My Mercedes shuts down non critical systems when voltage is low. Could the ignition switch be the problem. Also the passenger door lock actuator does not operate with key fob but usually does with button on console. I have checked all fuses in glove box and relays and fuses under the hood. Are there others I am missing. When this first started we replaced the brake pedal switch."

[wsmeyer]

Anybody have a spare LCM he can try?

[danewilson77]

That would be a nice troubleshooting option for sure.

[QC_ZHP]

I actually do. Let me know if its needed.

[brettbimmer]

I assume that the regulator was replaced with the alternator, thus ruling out that as a possible problem? Also, has he tried using different keys in the ignition to see if the problem happens with both? (I would guess that it would). Is the ground connection tight on the battery terminal itself? It seems odd that it is an intermittent problem and not one that occurs every time, hence my question on the ground wire connection.

[danewilson77]

Thanks fella's

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[wsmeyer]

I would change out the bulbs as well, kind of a long shot but cheap...

On our cars, the default is for the brake lights to be ON. When you first turn the ignition on, it does a "cold check" by sending voltage to the bulbs for .3 sec and measures the current. If it falls within the correct range it deems the bulbs working and turns control over to the brake switch. If not, you get the warning light and brake lights remain on. This is why LED's have to have the correct resistors to work or the "cold check" disabled in PA Soft. Also why a faulty ground causes the lights to remain on - the resistance isn't within the correct range.

All of this checking is done by the LCM so the problem could be there. He also mentions the windows not always working and those are controlled by the GM5 which is known to be flaky.

[NorCalZman]

Not to send you to another forum but I remember reading a few threads about this over at e46fanatics. I thought I recall seeing something about a ground somewhere being an issue.

[realdeahl]

Thanks for the info. I will pick up some new bulbs. They obviously are not burned out and all make good contact in the housing, but like you said it is a cheap test. Do I need to use BMW bulbs or can I pick up decent bulbs from AutoZone or Advance Auto?

This issue is crazy. The windows do work all the time, But the fault is more likely to happen if I open and close the windows with the engine off.

At lunch it took 6 minutes of idling before the issue resolved itself. So it goes like this.

Start car.
dash lights (taillights out) and brake lights on
Radio off.
All other systems normal.

After 6 minutes dash lights off and brake lights off
Airbag light briefly on then off.
Radio on
All Systems normal

It does not happen everytime I start the car now with the new battery and alternator.

My gut told me battery and alternator due to undervoltage. But both have been replaced. I even threw a charger on the new battery to make sure it was topped up.

I did the taillight ground repair last night and will double check it today when I get home. I maynot have good connections.

I mentioned the intermittent passenger side door lock actuator operation with Key Fob as another issue that is seemingly unrelated but perhaps not.

Thanks again for the help. I have been dealing with this for over a year now. Parked the car for a while because of the problems. I enjoy driving it much more than my gas sucking Tundra. Need it to be safe to drive.

[realdeahl]

The reman alternator came with a new regulator. BOSCH 120AMP. My wife and I drive the car using different keys. Same result. The battery terminal is tight. Just replaced the battery yesterday. I too am leaning now toward a loose ground somewhere, but where is the question?


I assume that the regulator was replaced with the alternator, thus ruling out that as a possible problem? Also, has he tried using different keys in the ignition to see if the problem happens with both? (I would guess that it would). Is the ground connection tight on the battery terminal itself? It seems odd that it is an intermittent problem and not one that occurs every time, hence my question on the ground wire connection.

[wsmeyer]

Thanks for the info. I will pick up some new bulbs. They obviously are not burned out and all make good contact in the housing, but like you said it is a cheap test. Do I need to use BMW bulbs or can I pick up decent bulbs from AutoZone or Advance Auto?

This issue is crazy. The windows do work all the time, But the fault is more likely to happen if I open and close the windows with the engine off.

At lunch it took 6 minutes of idling before the issue resolved itself. So it goes like this.

Start car.
dash lights (taillights out) and brake lights on
Radio off.
All other systems normal.

After 6 minutes dash lights off and brake lights off
Airbag light briefly on then off.
Radio on
All Systems normal

It does not happen everytime I start the car now with the new battery and alternator.

My gut told me battery and alternator due to undervoltage. But both have been replaced. I even threw a charger on the new battery to make sure it was topped up.

I did the taillight ground repair last night and will double check it today when I get home. I maynot have good connections.

I mentioned the intermittent passenger side door lock actuator operation with Key Fob as another issue that is seemingly unrelated but perhaps not.

Thanks again for the help. I have been dealing with this for over a year now. Parked the car for a while because of the problems. I enjoy driving it much more than my gas sucking Tundra. Need it to be safe to drive.


hmmm... the stuff I was saying about the cold-check is all from the notes in the BMW wiring diagrams, they are online here:

http://www.bmw-planet.com/diagrams/release/us/e46/index.htm

I'm almost certain that it is only done once when you turn the ignition on so that doesn't jive with what you just reported above in that the problem goes away by itself.

I'm leaning even more towards LCM but I wouldn't buy one of those without borrowing one first.

[Avetiso]

I have the same issue. Replacing lcm gets rid of it. I think there is a mistake in my coding I will address soon

Sent from my SM-G900T using Tapatalk

[realdeahl]

I have the same issue. Replacing lcm gets rid of it. I think there is a mistake in my coding I will address soon

Sent from my SM-G900T using Tapatalk

Is the LCM a DYI or do I need to go to an Indy shop or Stealership? What is the general cost?

[alexandre]

Is the LCM a DYI or do I need to go to an Indy shop or Stealership? What is the general cost?

$50 max for a used unit. Coding depends if you want to buy the hardware ($25) or have it done. 2 screws to remove in total, super easy.

[QC_ZHP]

EDIT: ^ beat me to it.


Is the LCM a DYI or do I need to go to an Indy shop or Stealership? What is the general cost?

Very easy to swap, but you'll have to get it coded to your VIN.

[realdeahl]

Is there any way to test the LCM to rule it out as a problem? Would a BMW code reader pull codes from a bad LCM?

[danewilson77]

Not to send you to another forum but I remember reading a few threads about this over at e46fanatics. I thought I recall seeing something about a ground somewhere being an issue.

This fella contacted me via pm at e46f.com. I didn't think he was getting the attention he deserved over there, as his issue wasn't solved yet.

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[BCS_ZHP]

An idea on possible bad ground - multiple things are being affected, not just the taillights. When under the car this weekend, there is a big ground cable and ground lug down near where you would change the oil on the passenger side. I noticed some corrosion on our ZHP although we're having absolutely no electrical gremlins at this time. Nonetheless, I cleaned it up for peace of mind. You might want to check that area to see if there is corrosion because it is fully exposed to the elements that hit the bottom of the car.

And welcome over here.

[KevinC]

Could it simply be a bad brake light switch at the pedal?

[danewilson77]

Posting for a friend. Any help/Idea's is/are greatly appreciated.

His quote:

"Still battling the gremlins. Changed alternator Saturday and installed a new AGM battery today. Car was fine leaving the battery shop. Came home opened and closed the windows with the car off and then started it. Damn brake lights light up and radio off. I'm about ready to drive it to a rough neighborhood and leave the keys in it."

"I replaced the fuses mentioned. Did the tail light ground. Replaced alternator and battery. The problem is intermittent but only happens when starting the car. It clears up after a few minutes sometimes and sometimes doesn't. Radio doesn't work when fault is present. That is what lead me to battery and alternator. My Mercedes shuts down non critical systems when voltage is low. Could the ignition switch be the problem. Also the passenger door lock actuator does not operate with key fob but usually does with button on console. I have checked all fuses in glove box and relays and fuses under the hood. Are there others I am missing. When this first started we replaced the brake pedal switch."


Could it simply be a bad brake light switch at the pedal?

Looks like this is what started it all....perhaps.

[toddness]

So - I joined the "brake lights on club" recently. Thought after reading about Dane's woes 15 months ago had me all sorted out with fuse #9.

My story goes like this - car had sat for a bit, killed my battery, pulled the battery and recharged it, reinstalled it and noticed all red in the rear on start. As the green indicator on the battery did not come back, and it was 8.5 years old, I chose to replace it with the 94R-DLG. Installed the new battery last night, still all red - then i read about dane's woes, swapped fuse #9 even though it looked good - still red. Then I am thinking, maybe I should have left the battery disconnected longer - so i do -still all red.

Such fun.

[derbo]

Could it simply be a bad brake light switch at the pedal?


This is my first gut feeling to check if the switch is good.

[danewilson77]

This is my first gut feeling to check if the switch is good.

OP...did you buy a BMW brake light switch or an aftermarket switch?

[toddness]

Bump - any updates

[KevinC]

One of my old Westmoreland GTI's had a bad switch at the pedal about a million years ago, causing the lights to stay on. Man were those poorly-built cars with crappy components! I'm guessing that may be the same issue here.

[Tnhl1989]

With NCSexpert you can reprogram the lcm to default. With PAsoft you can program vin and mileage. Either case I would try both.

[toddness]

So - I have this same issue. I just replaced the brake light switch with BMW replacement, power on car, brake lights still on. SMH.

If there was a fault somewhere, would the code readers find it?

[toddness]

bump for assistance...

[Avetiso]

Can't figure mine out either. I live with it.

"Arnold smoking a cigar in the Red Square; your argument is invalid." -Galaxy S5

[toddness]

Running around with my brake lights on all the time is really not an option.

I really hope I am not dealer bound.

[danewilson77]

Please check all 3 related fuses in glove box.

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[danewilson77]

I just received word tonight that a new ignition switch fixed this. $36.

[derbo]

Ignition switch. How interesting!

[toddness]

3 fuses ? I got # 9 which other two would these be ? I haven't seen reference to anything else brake related.

[danewilson77]

Think light related. I think I did 51, 9, and.....?

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[danewilson77]

Did you read my thread? I can't remember which of the three it was.

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[toddness]

I did - I thought #9 was going to be my savior and don't remember the other two. i am going back to look now. Thank you !

[toddness]

Fixed. I want to believe ground is involved.

Sequence of events.

Killed aging battery by letting car sit too long. recharge,
reinstall aging battery
discover issue for first time.
Battery lasts only another week while mostly sitting,
I am reading of possible electrical gremlins and exploring battery options.
replace battery (quick swap)
issue persists
remove ground for like an hour
issue persists
replace #9
replace brake light switch
issue persists
replace 9,32 and inspected so many more...(again today)
issue persists
rethink where this started with battery.
pull pos/neg let sit for 30, re-attach battery being more deliberate than ever in my application.
Problem gone.

I want to believe a code was thrown every time I installed or was a remnant of a previous installation being poorly done and not being cleared. I made sure those terminals were on there tight this time. I would have told you I had them tight previously...

Pissed. Probably wasted 37.00 on the brake light switch. Also curious, the existing switch had a spot of paint on it, while the replacement didnt. Interesting.

Aside - OEM battery post : 3405 - vin production date sept. 8, 2006 - the battery was like no more than 10 days older than the car.

[danewilson77]

Hopefully this stays fixed.

Samsung Galaxy S5...