Brake lights not functioning

[fantajuice]

The brake lights on my 530d (manual) '00 stopped working.
After the car died a few days back (fuel pump and after that the starter, replaced those and the BMW works again), the brake lights have suddenly stopped working. None of the 3 brake lights work.
I have checked the bulbs, replaced the brake light switch (already replaced it a couple months ago to try and fix the cruise control unsuccessfully) for a known good one and replaced the LCM. Fuses in the glove box are all okay.

Anyone happen to know what to check before I start pulling everything apart to run back the wires?

[MtnGn]

You might try file/ steel brush on connections and some di-electric grease. Probably not the solution, but worth a shot. When I have trouble with mine, its always the contacts.

[fantajuice]

Which contacts? Because the center brake light doesn't work either.

[sleuth255]

Ok, so assuming the car is not detecting burnt out bulbs in the brake lights, the problem has to be in the brake switch circuit. Interesting that you have been in there already.

[fantajuice]

Checked fault codes and got no faults in lights.
And pressing the brake, INPA showed that the brake switch worked.

[ross1]

So, you were having cruise control troubles related to this switch?
Have a look at the wiring diagrams and determine a commonality.

[fantajuice]

So, you were having cruise control troubles related to this switch?
Have a look at the wiring diagrams and determine a commonality.

No, not really, I was trying simple things that came to mind trying to fix the cruise control, because it doesn't engage with no related errors in any of the modules.

[Chedley]

Well, on the E39, the brake light switch does engage with a few modules -engine, transmission, ABS and LCM among others-. It actually does a lot more than turning on and off the brake lights. (See: https://www.bimmerfest.com/threads/b...r-abs.1355237/)

So , I'd check the switch and make sure it is the right one.
Note that it is very similar - but different in orientation, so not interchangeable- with the cruise-control switch that disables cruise when you tap on the brakes.

[edjack]

Chedley, post #5.

[sleuth255]

Checked fault codes and got no faults in lights.
And pressing the brake, INPA showed that the brake switch worked.

Well, you stumped this chump. Interested to learn what you eventually find out.

[Chedley]

Checked fault codes and got no faults in lights.
And pressing the brake, INPA showed that the brake switch worked.

Do you mean no "brake switch" error code (code 105 or 116) ? How does INPA shows you that the brake switch worked -- Educate us on this.

The brake lights on my 530d (manual) '00 stopped working.
....
I have checked the bulbs, replaced the brake light switch (already replaced it a couple months ago to try and fix the cruise control unsuccessfully) ....

Did the problem start after you replaced the switch to fix the cruise control -- but that did not fix it- ??

[fantajuice]

There are no brake light errors in the LCM besides automatic front light height adjustment (car originally came with xenons, no longer has xenons). INPA shows me the brake light switch working, as in when I open up the module and check live data, under digital values it shows the brake light switch on and off, depending on the brake pedal position.

I first noticed the problem after we had replaced the starter and the fuel pump in the fuel tank. Probably unrelated.

I know the brake lights are getting power, because in the LCM the option is toggled on for brake lights to work as normal tail lights, when both of the bulbs are seen as non-functional. And when I removed both of the bulbs - brake light lit up.
AND after I noticed that that works, we took out the brake light switch, crossed the wires for the brake lights and the brake lights lit up.
So I'm now convinced that I have to get an old mechanical brake light switch, because the more "modern" magnetic one doesn't work with my car anymore. Is that really my only option?

[fantajuice]

Found the issue. Under the driver's seat (LHD car) there's a bundle of wires, blue with a red stripe. The junction was completely corroded. I stripped the ends, twisted them all together and voilà - brake lights.