Brake LT Circuit error

[dmistry]

I keep getting the brake LT circuit error even though all the lights work fine. I have changed the brake light switch but still no joy. Any ideas ???

[Paul in NZ]

when you change the brake light switch DO NOT push the red retaining sleeve home...engage it the absolute minimum and the brake light switch is then self adjusting,i installed my first one like that (pushing the sleeve home)and it promptly destoyed itself the first time i braked hard....ding <brake lt circuit>When i bought the second one the service manager told me in no uncertain terms ......

[JAlfredPrufrock]

Can anyone tell me why this error will come and go?

[mikell]

The brake light switch is probably going. In my case, the brake light switch was intermittent for more than a year before I finally got over my lazy self and replaced the thing. One give away that the switch was going was that I could sometimes hear static when applying the brakes and listening to a waek AM radio station - basically, the switch was arcing. If the switch is good, try cleaning the contacts on everything in sight (even the light bulb sockets) with contact cleaner.

[Road_Carver]

I have that too, well after I fix my fog light it will come back :p I understand (the stealership guy told me) it is some kind of relay, sorry that is all I know, too many other things to fix 1st! :(


I keep getting the brake LT circuit error even though all the lights work fine. I have changed the brake light switch but still no joy. Any ideas ???

[timeout]

like I just posted in another thread, bulbs should be of the same brand and type. Apparently the resistance is measuered and compared between bulbs, any difference bigger than 3% (what I remember) will be reported as brake light error, etc.
On my car I could stop these false reports about brake lights, low beam and licence plate (all working) by replacing all bulbs. I dont know what was in there, but now its all one brand. Not one false alarm since.

The dealer probably meant the light control module, but its expensive and may not be necessary.

[Road_Carver]

I have that too, well after I fix my fog light it will come back :p I understand (the stealership guy told me) it is some kind of relay, sorry that is all I know, too many other things to fix 1st! :(


I keep getting the brake LT circuit error even though all the lights work fine. I have changed the brake light switch but still no joy. Any ideas ???

[JohnC]

how much did you guys pay for the switch. i got the message from time to time to, i might as well change it now

[Qsilver7]

resoldering all the joints in the LKM module has been known to cure the Brake LT Circuit module, too. So if switching bulbs and replacing the brake light switch still doesn't cure the problem...try resoldering the LKM (which is located in the front fuse box):

http://www.e32fixes.com/images/lkm_mustard/fusebox.jpg

What happens is, over time, the solder may get cracks not descerned by the naked eye...so resoldering the circuit board takes care of all the minute cracks etc:
http://www.bmwe34.net/e34main/maintenance/electrical/Data/LKM2.jpg

resolder all of the joints along the bottom (back side) of the LKM cirucit board...not just the ones circled in red:
http://www.e32fixes.com/images/lkm_mustard/lkm3.jpg

Here's instructions from Bruno's site:
* http://www.bmwe34.net/e34main/maintenance/electrical/LKM.htm

and another write-up:
* http://www.e32fixes.com/results.asp?method=show_fix&fixid=1

[MontesCarlos]

[QUOTE=I had the same problem. It seemed to have gone away unexplicably. I was getting the same message you were getting, and then I started to get parking light warnings too. For some reason when I replaced the parking light bulbs that were burnt out, the Brake Lt circuit message went away. Some times I think that the Clifford alarm system that's installed in my car may be affecting the light sensing circuits in the LKM[/QUOTE]