Dreaded Brake Light Circuit error, Lets Re-engineer!!

[kenehresman]

Ok, so If I understand this all correctly, and the CCM received a signal from the LKM that the lights are not functioning correctly, a simple and permanent fix for the dreaded brake light circuit error would be to locate the appropriate resistor inthe LKM that is responsible for raising or lowering the open circuit resistance value that trips the light right??

Anyone know what resistor this is? or have a COMPLETE LKM schematic?

Since basic ohms laws apply to all these circuits, I don't think Hanz had his own laws of electricity simpley piggy backing the right resistor, (fixed or variable) either on top of (parallel to) or in circuit with (serial) will allow us to manipulate this circuit....

Anyone's thoughts?

The other option, is to hardwire the input to the CMM on the brake light circuit (pin 7 I think on the X19) to either a logic high or low depending on what sets this error...

[winfred]

change the brake light switch, this does the trick on probably 99% of the cars

[snopro67]

Ditto on the brake light switch, both my BMW's had the brake light switch changed before 70K miles.

[snopro67]

Here are some pics of my '97 M3 brake light switch (old) after I gutted it to look inside to see what the problem was:


this side must not have much amp load (switch has 2 poles)
http://i174.photobucket.com/albums/w106/snopro67/6ee469b2.jpg


this side obviously takes the load of the stoplights
http://i174.photobucket.com/albums/w106/snopro67/5d01f76f.jpg

[kenehresman]

um.... I did that, it was the first thing :-)) I had a electrical switch proximity type and replaced it with the mechanical clicker....

[cooljules]

um.... I did that, it was the first thing :-)) I had a electrical switch proximity type and replaced it with the mechanical clicker....
i sometimes get this on my 525i touring, i had read about it, before it happend to me....anoying

[shogun]

LKM pinout of the LKM-L and -B is here on the German board
http://www.7-forum.com/forum/showthread.html?t=52455&highlight=LKM

Note that the European design LKM has more relais inside, US design has 3 and the rest of the world has 4, because they have the additional one for rear fog lights.
And here I posted the pinout also on the Bimmerboard
http://www.bimmerboard.com/forums/posts/255204/

[Blitzkrieg Bob]

that is not a BMW one, you'll probably still get the error.

The CCM is very sensitive to resistance and changes in contacts points, bulb sockets etc. will throw an error.

[bmwrp8]

happen to me before...just change the brake switch easy to do