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General E46 Forum
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Old 04-13-2017, 12:55 PM   #21
jdstrickland
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I wish the schematics were better so I could give tips on what to check and where to check it.

I have the uncomfortable feeling that you have a defective switch. What happens if you unplug the switch?

Never mind, INPA sees that the switch is working, so unplugging it should not tell you anything, that is the lights should remain on. All indications are the LCM. Good luck.

Except for the ability to program the lights, I do not understand why the brake circuit goes to the light switch. It's nonsensical to me that the brake light circuit goes to the lighting control module.
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Old 04-13-2017, 01:05 PM   #22
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Do you have factory LED tail lights?
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Old 04-13-2017, 03:00 PM   #23
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Quote:
Originally Posted by jdstrickland View Post
I wish the schematics were better so I could give tips on what to check and where to check it.

I have the uncomfortable feeling that you have a defective switch. What happens if you unplug the switch?

Never mind, INPA sees that the switch is working, so unplugging it should not tell you anything, that is the lights should remain on. All indications are the LCM. Good luck.

Except for the ability to program the lights, I do not understand why the brake circuit goes to the light switch. It's nonsensical to me that the brake light circuit goes to the lighting control module.
Thank you for the help you are trying to give me.

Here is some schematics I have been able to find.




What I understand from them is this :

Fuse 9 -------> Brake Light Switch |----> LCM -----> Tail light and center brake light
| ----> DDE
Do you agree with my understanding ?

So checked fuse 9 he is good, checked and even replaced brake light switch, he is good.
This leaves LCM or DDE.
I don't think it is the DDE cause when the brake switch is failing (according to the BMW documentation I found here http://www.meeknet.co.uk/e38/E38_Brake_Light_System.pdf) the cruise control is deactivated. But mine is working perfectly.

I ordered the LCM, hope he is the failing part.

Do you agree with this logic ?

Last edited by pool0513; 04-13-2017 at 03:33 PM.
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Old 04-13-2017, 03:03 PM   #24
pool0513
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Do you have factory LED tail lights?
Hello,

My car is a 3 hand car. When I bought it, it had the led tail light.
But I don't think it is factory, as according to my VIN all documentation shows classic tails not led ones.

But the led one where working, until some moment (I don't know exactly when, cause I noticed the problem when some driver told me on the road).

My actual tail light are OEM.
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Old 04-13-2017, 03:19 PM   #25
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Quote:
Originally Posted by pool0513 View Post
Hello,

My car is a 3 hand car. When I bought it, it had the led tail light.
But I don't think it is factory, as according to my VIN all documentation shows classic tails not led ones.

But the led one where working, until some moment (I don't know exactly when, cause I noticed the problem when some driver told me on the road).

My actual tail light are OEM.
Consider replacing with classic tails?

Last edited by SSchwab; 04-13-2017 at 03:20 PM.
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Old 04-13-2017, 03:24 PM   #26
pool0513
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Consider replacing with classic tails?
Why would I do that ?
Mine were working fine.
I don't want to change them, I want to find the issue and fix it
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Old 04-13-2017, 03:30 PM   #27
SSchwab
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You may need a reflash by a dealer or shop with the right equipment.
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Old 04-13-2017, 03:31 PM   #28
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And I generally prefer to keep my BMWs original.
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Old 04-13-2017, 03:35 PM   #29
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You may need a reflash by a dealer or shop with the right equipment.
Yes I agree with that.
But my LCM is already flashed for led tail mod.
And no need to dealer, NCSExpert and 5 minutes of time and it's done.
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Old 04-13-2017, 03:37 PM   #30
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And I generally prefer to keep my BMWs original.
Agree with you 100%.
But in this case, BMW started to put LED tails on this model starting on 2006.
Mine is 2004, and nothing have changed between them. Just the pin clip and the LCM coding.
This is not a major mod, this have been done by a lot of people, and there is a lot of DIY for doing it on the internet.

I don't think this is a big deal that would put the car or the driver in danger.

Last edited by pool0513; 04-13-2017 at 03:38 PM.
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Old 04-13-2017, 03:42 PM   #31
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Originally Posted by pool0513 View Post
But in this case, BMW started to put LED tails on this model starting on 2006.
Interesting; they started putting in LEDs in 2004 here in the States.

Not that this has any bearing on what you're talking about... carry on!
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Old 04-13-2017, 04:40 PM   #32
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Where did you get those schematics??


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Old 04-14-2017, 04:19 AM   #33
pool0513
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Where did you get those schematics??


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Hello,

It's with the search function of INSTA.

Google for INSTA-D (Rheingold).
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Old 04-14-2017, 11:54 AM   #34
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As for replacing the brake lights back to factory condition,
I would accept this if the failure began with the installation of the lamps you have now. If you bought the car with the lights that are in it, and it was good until now, then the lights are not the problem. Having said that, there is value in replacing the lamps as a diagnostic test. I would expect the problem to persist regardless of the type of lights that are installed. But at this point swapping the lights as a diagnostic test might find that the lights themselves are giving you trouble.
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Old 04-14-2017, 12:12 PM   #35
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As for the Fuse,
The lights are on so the fuse has to be good. A failed fuse will never cause a circuit to be active -- lights on -- all of the time. I suppose there could be a reverse polish kind of circuit that is held off by a relay and a failed fuse could change the state of the relay and turn something on. But, think of the purpose of the fuse. It's job is to protect the wiring from a short. The fuse blows if there is a short, and this prevents the wire from melting and perhaps setting fire to the car. There's no practical purpose in having a failed fuse bring a circuit alive somehow.

If the lights are on, the fuse is good. If the lights never come on, then the fuse might be bad. When a load does not come on, check the fuse. When the load does not go off, the fuse is never the problem.

Schematics
I have the Bentley Manual with the same schematics. The Exterior Lighting schematics of the E36 (all schematics of the E36, for that matter) are far superior for tracing the circuits than the schematics of the E46. The schematics of the E46 are black box diagrams, the E36 shows the components in many cases, at least one can trace where the signals go into a module and follow the path to where it comes out, the E46 just has the wire go to the module and then disappear.
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Old 04-14-2017, 02:12 PM   #36
pool0513
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Originally Posted by jdstrickland View Post
As for the Fuse,
The lights are on so the fuse has to be good. A failed fuse will never cause a circuit to be active -- lights on -- all of the time. I suppose there could be a reverse polish kind of circuit that is held off by a relay and a failed fuse could change the state of the relay and turn something on. But, think of the purpose of the fuse. It's job is to protect the wiring from a short. The fuse blows if there is a short, and this prevents the wire from melting and perhaps setting fire to the car. There's no practical purpose in having a failed fuse bring a circuit alive somehow.

If the lights are on, the fuse is good. If the lights never come on, then the fuse might be bad. When a load does not come on, check the fuse. When the load does not go off, the fuse is never the problem.

Schematics
I have the Bentley Manual with the same schematics. The Exterior Lighting schematics of the E36 (all schematics of the E36, for that matter) are far superior for tracing the circuits than the schematics of the E46. The schematics of the E46 are black box diagrams, the E36 shows the components in many cases, at least one can trace where the signals go into a module and follow the path to where it comes out, the E46 just has the wire go to the module and then disappear.
Hello,

You are absolutely right about the fuse purpose.

But like me, you don't have a dutch brain lol !

If the fuse number 9 in the E46 go down, the brake light stay ON until the fuse is replaced. It's the same for the brake light switch.
This is done in the purpose to let you know that you have a failure in the car and you must fix it to make the light go off.

Yes it's weird, but it's how it works. Trust me I have done my homework

There is a post on this forum were someone reported this.
Give me 5 minutes and I will find it.

Last edited by pool0513; 04-14-2017 at 02:12 PM.
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Old 04-14-2017, 02:16 PM   #37
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here it is :

http://forum.e46fanatics.com/showthread.php?t=843170

Check post #12 and #14 and of course the first one.

Same issue as me, and it was fuse 9...

Dutch mind =

Last edited by pool0513; 04-14-2017 at 02:21 PM.
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Old 04-16-2017, 02:41 PM   #38
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Originally Posted by pool0513 View Post
It's with the search function of INSTA.
Google for INSTA-D (Rheingold).
Thanks so much! Agh, will make my wiring research so much easier
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Old 04-17-2017, 12:03 PM   #39
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Originally Posted by pool0513 View Post
Hello,

You are absolutely right about the fuse purpose.

But like me, you don't have a dutch brain lol !

If the fuse number 9 in the E46 go down, the brake light stay ON until the fuse is replaced. It's the same for the brake light switch.
This is done in the purpose to let you know that you have a failure in the car and you must fix it to make the light go off.

Yes it's weird, but it's how it works. Trust me I have done my homework

There is a post on this forum were someone reported this.
Give me 5 minutes and I will find it.
Hello sir, You get this sorted yet? got factory set of lights at the rear and have the same issue.....replaced/removed fuse 9 and the 3 rear lights are on regardless, not got round to replacing the brake switch yet or doing any diags as you have.....but can we categorically say that a failed brake switch keeps the rear brake lights on as default? personally I dont get it? i thought by removing fuse 9 the circuit will not be completed and hence not lights....?
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Old 04-17-2017, 04:17 PM   #40
pool0513
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Hello sir, You get this sorted yet? got factory set of lights at the rear and have the same issue.....replaced/removed fuse 9 and the 3 rear lights are on regardless, not got round to replacing the brake switch yet or doing any diags as you have.....but can we categorically say that a failed brake switch keeps the rear brake lights on as default? personally I dont get it? i thought by removing fuse 9 the circuit will not be completed and hence not lights....?
Hello,

Nop I still did not solved this problem. I am waiting for the LCM I bought.
I hope he is the guilty part here.

What I can tell you for sure :

Fuse 9 dead = Brake light ON always (As soon as you turn the ignition to position 1)
Brake Light switch dead = Brake light ON always (As soon as you turn the ignition to position 1)

Why the brake light will be ON if the brake light switch is faulty ?

The brake light switch is not a traditional switch, it's a hall effect one.
When the pedal is released, there is contact between the metal of the pedal and the switch. This contact is activating the switch, and he sends a signal to the LCM.
This signal tells the LCM that the brake pedal is not pressed and turn off the brake light.
If there is no contact between the pedal and the switch, then there is no more signal sent to the LCM and he turns ON the brake light.
With this kind of switch we talk about software controlled light.
Traditional switches are mechanic, when you press or release the pedal, the switch close or open a circuit.

Why the brake light will be ON if fuse 9 is dead ?

Almost same as the other one, no fuse 9 means no more brake signal to the LCM then equal brake light ON.

Hope I answered your question

Now I'm gonna try to help you.

If you do have INPA you can test your brake light switch.
If not you have two other solution :
- Do you have cruise control on your car ? If yes and you are able to use it, it means that the brake light switch is ok. If the brake light switch is dead, you can't use cruise control anymore. This is done for obvious security reason.
- This one is a bit hard for me to explain as English is not my actual language. So let's try. In fact the brake light switch is in a small squared plastic piece that hold him, and gives you the ability to adjust the switch. Take the switch out of the plastic piece but don't disconnect it. Take a metallic piece (a screwdriver will do the job) and put it on the switch. If you do it well, the magnet of the switch will attract the metallic piece. And you will heard a relay changing state (clic). Remove the metallic piece and you will heard the relay changing again (clac). Do it multiple times and you will heard clic/clac/clic/clac. If you heard the clic/clac then the switch is ok. For you to know, it's the ABS protection relay that is activating itself because you are not really pressing the brake pedal, (I'm not sure of what follow) so the brake fluid is not moving and the ABS protecting it self.
After a lot of search, I think my issue is the LCM. But I cannot be 100% sure because I still didn't receive the new one (ordered on ebay UK) because of bank days.
I really hope he is the faulty part, cause if he is not, I am going to cry a lot and then I will put fire to the car


I have a question for you, when you turn the ignition, the brake light turn ON immediately or is there a small timeout (like 2 sec) ?
Personally I have 1 or 2 sec timeout between the time I turn the ignition and the time brake light become ON.

PS : All of what I say here is based on what I learned about my car which is a 2006 330CD. You have to check if this information applies to your car.

Last edited by pool0513; 04-17-2017 at 04:20 PM.
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