My 2002 Cooper S had a problem with the brake lights permanently being on.
After some searching I found that the probable cause was a bad diode.
Here's what I did:
Remove plastic cover running along sill and underneath passenger footwell.
You should be able to just pop it of, there are no screws just friction fit trim fasteners. You should see the BCM unit and a couple of wiring looms.


Below the BCM is a wiring loom with a small white plastic box that contains a diode. You may have to unravel some black cloth tape to expose the white plastic box.


Peel back the rubber boots on either end of plastic box to expose two connectors. Unplug these and you will be able to remove the diode and the two spade connectors.

Once you open the white box you will find a diode that has a female and male spade soldered to it. Examine the diode carefully and you should see one end has a silver band, note which connector this silver band is connected to. In my case it was the female spade with the silver band end soldered.


I elected to change the diode for the closest match I could find immediately , you may want to order the exact same diode Silicone Rectifier 1N5626

Using a soldering iron I removed the damaged diode and soldered in my new diode. In order to correctly size the diode and connectors note the overall size of the existing diode.

 

Place diode in box and pack with Dielectric grease to protect it from water.






The only tool needed for this job is a soldering iron.
Will report back if there are any issues with non-exact diode.

 

p.s. Does anybody know why the soundproofing/foam gets wet in this area? And how to fix it?

 

My car has this exact problem. thanks for the report.
time to get a diode.

 

Sorry to raise this from the dead. But discovered my lights staying on today. Took me all of 5 minutes to get the diode case out and discover it was destroyed. No clue how long this issue has been present, but a month ago my sunroof drain on the passenger side needed replacing as it leaked. So I assume this is a product of that.

I'd suggest anyone who has a leaking sunroof have a friend check your brake lights. This is a very easy problem to go undiscovered.

Now I'm headed to radio shack to buy a 600v 3amp diode. I highly suggest doing a DIY. Repair instead of shelling out the $28 for the BMW part. The diode is a buck at Radio Shack.

 

Yes, dug up from the dead but a good thread.

Look at the connection of the BCM and make sure there is no corrosion from the sunroof leak. Otherwise you can get crazy light and control functions.

Other thing for the rear brake light is on is the stop light switch sticks: 61316967601

http://www.ecstuning.com/Search/SiteSearch/61316967601/




So its good to check that also.

 

I'm still trying to diagnose this brake light thing on mine...I have a 2005 MCS and I've checked the BCM area and it's always dry and clean.

I can't find this diode for the life of me. I removed the large trim panel, looked around, no diode anywhere.

I am not kidding when I say my Mini looks new, there's not a spot of water/oil/dirt anywhere in there. I wish I could find this diode because I do have issues with the door locks not working when this happens. But I can't find it...do not all R53 have the diode?

 

It's there somewhere. Prob wrapped in black tape somewhere. But mine was right near the BCM. It took me all of 2 minutes to remove the trim, locate the diode and remove it.

 

Thanks. Last I heard it was 8-10" back on the loom going down the passenger sill but nothing there. If yours was right near BCM mine could be too. I'll have to go in and look. I think my issues are worse when I turn the car off with my foot on the brake, which hopefully points to this diode.

On another note what are those wires that are screwed to the metal on the door sill under the cover? They don't look like a ground but like sensors of some kind...

 

Yeah. I found mine right near the BCM. And I know at you're talking about. But no idea what they are. They almost look like a ballast resistor of some kind. Def not grounded. It's painted.

 

Still can't find the damn diode. I've got the BCM out, it seriously looks new, zero sign of water, the Mini looks new under the carpet too:





My next thing to think about before having the BCM checked out at a shop is to look at the ignition switch. Often when my brake lights are on the ignition beeps as if the key was still in, when it's not. And then the keyless entry won't work sometimes too. I've read BMW ignition switches of this era cause all kinds of gremlins, and someone on the other board fixed the stuck brake lights doing that, so I'm going to check that somehow...

 

Any update ?

 

Thanks for looking, but I've been out of town and had no time. Seemed to be a little better for a day or two after I had the BCM out but then today it's gone back to the weird behavior.

No sign of that diode anywhere. I've read that it may have been integrated into the BCM at some point which is unfortunate. The inside of the BCM looks perfect...brand new like you see in the pics. I'm baffled as to how that could be malfunctioning, it's never been wet and people that do get them wet can even survive...

 

Welcome.

I would check the wiring harness and looks for slices or damage in the cable. Since everything else looks fine.

 

Well I finally woke up to a dead battery. NO idea if the brake lights killed it or what, though I did notice they would say on longer and longer as the days went by. Maybe they stayed on overnight that time.

Just realized, that I totally forgot to mention...I had installed one of those airbag modules from eBay that turns off the light for the passenger seat sensor malfunction. I disconnected the battery and took that out before jumping the car. It runs great but seems like the battery doesn't hold much charge (doesn't stay above 12V) though it starts the car (but a bit slow cranking). The alternator did test OK at 14V when the car was running when I had them check battery.

My multimeter is broken now, so I'm having AAA come by for a battery/charging system test and possibly (likely) install a new battery.

In the last couple of days since I removed the airbag module thingie, it hasn't done anything weird...so crossing my fingers a new battery and removal of that airbag module fixes things....

 

Bumping another old thread...

I have the same problem. I have a 2006 non-S and I can't find the diode, and ended up stripping basically all of the cloth tape looking for the damn thing. Perhaps it's different post-facelift. I found that the only way to get the lights unstuck is to insert the key to position 2 without starting the car, then position 0, then position 1, then position 0 and removing the key. It's as if this motion resets the computer or something. Let me know if you've made any progress since your last post!

 

Yeah mine was fine after I removed the airbag sensor module. The bag got replaced under the recall and I didn't have an issue after that. Never found the diode in my 05 guessing the design had changed by then.

 

Ok, I'll try that. Thanks for confirming!

 

Unfortunately, unhooking the airbag module didn't solve my problem. My F40 fuse also keeps blowing, and the module is on that circuit, so I thought there might've been a short. Back to the drawing board...

 

I’m ordering the diode now. Should the battery be disconnected. ?

 

Brake light stays on Hello I have a mini 2002 I have a problem with the brake light That remains lit that a key is inserted I buy unit brakes It did not fix the problem I replace the burnt diode Still left on What to do H E L P

 

Brake light stays on Hello I have a mini 2002 I have a problem with the brake light That remains lit that a key is inserted I buy unit brakes It did not fix the problem I replace the burnt diode Still left on What to do H E L P

 

I have the same problem since almost a year ago. I went and bought a new diode and the guy in the shop said that it didn't matter if I got 800v instead of 600v. Is that true? I changed the diode and soldered it but it still doesn't work and I'm also confused if I put it in the right direction.... The one that was destroyed had the letters straight so you could read them so i figured it would be the same with the new one. Can I use a multimeter fo find out? And I hope you're problem is solved. =)

 

I know this is an old thread and has revived a couple times. I have an 05 R53 that the brake lights are staying on. Before that happened I had some cluster issues, speedo and tag (gauge package so speedo and tach are over the steering wheel) where working intermittently and then finally stopped all together and now all of the dash lights are out with no blown fuses. After my speedo tach and dash lights went out was when I noticed the brake light. Everything works fine with ignition on but when the ignition is off the brake lights are on. I went on vacation last week, when I got home and got in my car there was a couple of inches of water in the drivers floor. I assume my issue is a corrosion problem but I have removed all the water, dried out and pulled every plug apart, cleaned and added dielectric grease to. I have not seen any corrosion anywhere. The passenger side of the car is dry, bcm dry as well as all of the connectors over there. No diode in this model, I read that the newer (im guessing facelift models) the diode was intergraded into the BCM. Would all of this water cause internal failure in the BCM? I removed the BCM and took off the cover and everything "looks" perfect. I have looked over all of the harness I can see and checked my grounds inside and I have not found anything. Any help would be greatly appreciated.

 

Where can you get the part?? I know that I can make one but I couldn't find one online.
Thanks