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  #1  
Old 04-Apr-2013, 02:41 PM
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Default E46 Airbag DashLight question

Hi There,

I am at that stage that i am really desperate of understanding what the issue is whit this airbag error on the dash.

I just failed the NCT twice (the guy that had the car before had a peace of black tape covering the dash light so first time it wasn't working at all. The second time because it was on when the car was running..) because of it and i am no where near close to solving the problem...

I have checked all airbags are connected and none of them is missing, i also connected the Passenger sensor under the the seat as it was disconnected, i did absolutely every possible fix i could find around the forums, and yet the still get the light to go off. ( can it be a case where you need to reset the code now using a diagnostic tool?)

I dropped the car in the garage before all of the above, and what they told me is that they need to change the entire power cable ( the positive one) that runs from the battery up to the engine to have it fixed ( according to their diagnostic tool it was a "connection error" ( which can be explained by the fact that the passenger seat sensor was not connected at all)). They priced me 700 euro for that cable, excluding labour ( prob. 2 hours) and VAT ( so it might jump to 1K+).

Browsing here and there looking at all error codes i haven't seen any one mentioning this type of fix, it usually is something to do with the passenger tension mat or the seatbelt pre-tentioner or faulty wires under the seats.

Before i go and sped 1k on what is supposedly the issue i really want to ask if some had / heard of this type of problem before?

I would say it might be possible if you smashed the car or anything, but mine has never been hit and none of the airbags ever exploded so i think that it might be something very easy to fix? I just order a reading tool so i can better understand the error code myself but surely (from what i have been reading) no one had that issue before that you need to change the entire power cable.

Any help / tips appreciated.
Thanks,
Niko
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  #2  
Old 04-Apr-2013, 02:55 PM
Ford 2 Ford 2 is offline
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Well there's a way you can pass the nct for 0 outlay..bag will still fire in a accident etc..just take out the clock and wire the bulb to the abs light. It will then mimic that and come on and go off..save yourself from going mad
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  #3  
Old 04-Apr-2013, 03:00 PM
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Seems as great idea And will definitely try if i cant get it fixed you know for less than 1k.. My main concern though is what the garage told me. I use these guys a lot and if they are "fixing" something that is working and the error lies somewhere else it would definitely raise some questions
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Old 04-Apr-2013, 03:20 PM
rebel.ranter rebel.ranter is offline
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The component that your garage are saying that needs to be replaced is the Battery Safety Terminal or BST. This unit has a pyro charge on it that detonates in the event of the crash. The detonation disconnects the main battery cable from the battery cutting the engine out but leaves a smaller cable attached to allow hazard light to work & central locking to pop open.

Every unit in the Multiple Restraint System (MRS) reports a resistance value to the Airbag conrol unit (MRS unit). The values are typically between 3-5ohms. If the control unit detects a reading either more or less than this value from any of the units connected then an error code is thrown. The connected units include:
- BST
- Airbags
- Crash sensors

Did they tell you the exact code that was thrown? It seems as though they have honed in on the specific item (BST) so they must be using some reasonable diagnosis solution. Did they say the error said resistance too high or too low? There is a yellow or grey cable (see yellow connector with thin cable in the picture below) going in to the battery terminal & this can sometimes get disconnected, this will give a "resistance too high" error, check to see that it is plugged in.
If there is a "resistance too low" error then the internals of the BST unit have failed. I won't advise this but you could put a 3ohm resistor in line with this yellow cable to fool the MRS unit in to thinking that the BST is alright. Or course in the event of the crash it would be unknown what would happen with the pyro in the BST, your engine might not cut out.
You could look at sourcing a 2nd hand BST cable, on EBay they are there from €110 to €160:
http://www.ebay.ie/sch/i.html?_trksi...at=0&_from=R40





Good luck.
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Last edited by rebel.ranter; 04-Apr-2013 at 03:32 PM.. Reason: add picture & pelling!
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  #5  
Old 04-Apr-2013, 03:27 PM
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Here's an example of just some of the erros that an MRS can report. This just to give you an idea that it's not just as vague as "airbag light on", "airbag light off". Deeper troubeshoting can be done.

Quote:
E R R O R M E M O R Y R E P O R T
-------------------------------------
Date: 10/25/12 16:06:04
ECU: MRS4
JobStatus: OKAY
Variant: MRS4
-------------------------------------------------------------
RESULT: 10 errors in error memory !
-------------------------------------------------------------
97 Buckle Passenger
Error frequency : 1
Error not currently present
Battery short circuit / (Wiring) break / Resistance too large
Error not sporadic
-------------------------------------------------------------
96 Buckle Driver
Error frequency : 1
Error not currently present
Battery short circuit / (Wiring) break / Resistance too large
Error not sporadic
-------------------------------------------------------------
5 Ignition circuit ZK4 / Side airbag front left
Error frequency : 1
Plausibility error
Error not currently present
Error not sporadic
-------------------------------------------------------------
4 Ignition circuit ZK3 / Airbag Passenger Stage 1
Error frequency : 1
Plausibility error
Error not currently present
Error not sporadic
-------------------------------------------------------------
1 Ignition circuit ZK0 / Airbag Driver Stage 1
Error frequency : 1
Plausibility error
Error not currently present
Error not sporadic
-------------------------------------------------------------
134 MRSA front right
Error frequency : 1
Error not currently present
Programming unsuccessful
Error not sporadic
-------------------------------------------------------------
132 MRSA front right
Error frequency : 1
Plausibility error
Error not currently present
Error not sporadic
-------------------------------------------------------------
131 MRSA front left
Error frequency : 1
Error not currently present
Programming unsuccessful
Error not sporadic
-------------------------------------------------------------
129 MRSA front left
Error frequency : 1
Plausibility error
Error not currently present
Error not sporadic
-------------------------------------------------------------
240 Internal error
Error frequency : 1
Error not currently present
Error not sporadic
================================================== ===========
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  #6  
Old 04-Apr-2013, 03:37 PM
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sounds like they dont know what they are talking about. connection error may mean that there is no communication with the airbag control unit. Different diag systems will have different ways of discribing faults so you may be getting dragged up the garden path. You shouldnt really expect the light to go out by playing with a few connectors at random according to forums. Step one should be to get the event memory checked by somebody who knows these cars well enough to be able to make an accurate diagnosis.
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  #7  
Old 04-Apr-2013, 03:39 PM
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Quote:
Originally Posted by rebel.ranter View Post
The component that your garage are saying that needs to be replaced is the Battery Safety Terminal or BST. This unit has a pyro charge on it that detonates in the event of the crash. The detonation disconnects the main battery cable from the battery cutting the engine out but leaves a smaller cable attached to allow hazard light to work & central locking to pop open.

Every unit in the Multiple Restraint System (MRS) reports a resistance value to the Airbag conrol unit (MRS unit). The values are typically between 3-5ohms. If the control unit detects a reading either more or less than this value from any of the units connected then an error code is thrown. The connected units include:
- BST
- Airbags
- Crash sensors

Did they tell you the exact code that was thrown? It seems as though they have honed in on the specific item (BST) so they must be using some reasonable diagnosis solution. Did they say the error said resistance too high or too low? There is a yellow or grey cable (see yellow connector with thin cable in the picture below) going in to the battery terminal & this can sometimes get disconnected, this will give a "resistance too high" error, check to see that it is plugged in.
If there is a "resistance too low" error then the internals of the BST unit have failed. I won't advise this but you could put a 3ohm resistor in line with this yellow cable to fool the MRS unit in to thinking that the BST is alright. Or course in the event of the crash it would be unknown what would happen with the pyro in the BST, your engine might not cut out.
You could look at sourcing a 2nd hand BST cable, on EBay they are there from €110 to €160:
http://www.ebay.ie/sch/i.html?_trksi...at=0&_from=R40





Good luck.
Well if they were so nice to explain it as you then it would have made more sense in what they actually told me they need and i wouldn't have questioned it
Now it makes a bit more sense, the chap that had the car before did some extremely weird DIY fixes that were totally baffling. The small back cable with the yellow connector on the end (excuse me not knowing the terms, quite knew to this :blush: ) was cut in half ( why? no one knows) i manage to get that one replaced with a new one.
The error code they tend not to say what exactly is in case you want to just diagnose your car and then go fix it yourself (which make sense). The tool they were using was massive it kinda looked as a briefcase and they specialise in BMW, and the only thing he said is and i quote " The tool keep saying connection error, connection error" ( which is why i though well the tension mat under the passenger seat was disconnected so it make sense to show this error) So far they were never wrong in anything they said / fixed and i really have hard time believing that this power cable can cause such an issue ( now that i know what it actually controls it makes way more sense to trigger an error light).
Thank you very much for the explanation at least it brought some more confidence back i will see if i can try and find a cable, in any case i wouldn't mind paying as far as i know that i am not being screwed...
Cheers Man!!!!
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  #8  
Old 04-Apr-2013, 03:47 PM
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Quote:
Originally Posted by the situation View Post
sounds like they dont know what they are talking about. connection error may mean that there is no communication with the airbag control unit. Different diag systems will have different ways of discribing faults so you may be getting dragged up the garden path. You shouldnt really expect the light to go out by playing with a few connectors at random according to forums. Step one should be to get the event memory checked by somebody who knows these cars well enough to be able to make an accurate diagnosis.
Completely agree there i have no intention of playing mechanic What i was checking is just the basic stuff, the seats were changed in the car so i though that there might a cable that was not correctly plugged, and that the fuse was alright. I do not dare messing with the electric of the car, i was only trying to understand if the entire cable needs to be replaced why would it give an Airbag Error
Bringing it to the garage tomorrow morning to get it sorted.
Cheers Folks!!
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  #9  
Old 04-Apr-2013, 11:30 PM
michael320 michael320 is offline
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I may have a BST cable lying about il have a look and let you know, there are instances where the BST cable can blow if someone jumps the car off directly off the battery also so keep that in mind.

Different diagnostic devices will show different descriptions, some refer to it as a battery isolation switch or something to that effect.

If your stuck let me know,I can plug it in for you and see what happens.

With regards to price the guy who quoted you is a complete goon, the cable can be bought from bmw for around 350 euro, its a repair section and takes no more than 40 mins to fit.
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  #10  
Old 29-Dec-2013, 11:43 AM
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Default airbag restraint system faulty - bmw 320i 2005

please find attached the pic

can anyone kondly help ?

cheers
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