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      09-11-2017, 02:31 PM   #1
One28Goat
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Replacing 128i airbag. How to know it wont be triggered instantly?

Hey, I am replacing the steering wheel airbag on my 128i. It was in a front end collision and I want to make sure the bag doesn't deploy as soon as I connect it.

Does anyone know or have any guides or links? All I can find is takata recall articles. Or is this something I really shouldn't be worried about?
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      09-11-2017, 04:11 PM   #2
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IME, when there is a collision and a/b deployment you'll need to replace all the items involved. Noted, I have no BMW experience in this but for the major manufacturers I've worked for, after deployment you'll need to replace the associated belts/buckles/unit, etc. Again i'm not sure if this applies to us here but it's something to verify.
Now, I've never heard of a deployment without a collision sensor command so what you're suggesting is extremely unlikely. The bag should be mostly plug and play but getting the SRS warning off is another story.
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      09-12-2017, 07:15 AM   #3
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Correct. If you need to replace the steering wheel airbag, you must replace the steering wheel also - because the heat deforms the metal.

If the passenger airbag in the dash deployed then you need to replace the dash.

Usually if the driver bag deploys then you'll also find the seatbelt female buckle pretensioner is also deployed.

We usually only disconnect the negative battery terminal then wait a minute, discharge any static in our body then carry out the work.
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      09-12-2017, 10:38 AM   #4
One28Goat
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Great, thanks for the info. I just wanted to make sure it wasn't telling the airbag to deploy still before I pluged in a new one.

I have already replaced the belt tensioner and pretensioner and will be installing them soon too. I'll have to check the steering wheel I inspected the back plate and didn't see anything. Seems to turn fine as well. I'll check for fit and connection issues with the bag in as well.

The srs computer "should" be clear-able by my bmw specific scan tool from what I've read otherwise I'll have to take it to my local import shop and see if they can or get a BavTech. Probably still cheaper than getting the dealer to clear them.
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      09-12-2017, 10:45 AM   #5
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You will also have to replace all the triggered impact sensors.
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      09-12-2017, 02:08 PM   #6
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Quote:
Originally Posted by MightyMouseTech View Post
You will also have to replace all the triggered impact sensors.
Definitely. Most likely the SRS control module will need to be replaced as well. Those codes cannot be cleared and upon deployment the module trips a relay inside itself that renders it inop. There are places that will "fix" it but no guarantees there. The OEM instruction is always to replace.
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      09-12-2017, 02:36 PM   #7
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If you have INPA, you could reset the error codes and it will get rid of your srs light.
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      09-12-2017, 03:41 PM   #8
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Quote:
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Quote:
Originally Posted by MightyMouseTech View Post
You will also have to replace all the triggered impact sensors.
Definitely. Most likely the SRS control module will need to be replaced as well. Those codes cannot be cleared and upon deployment the module trips a relay inside itself that renders it inop. There are places that will "fix" it but no guarantees there. The OEM instruction is always to replace.
Was not sure about BMW, I know with Honda, once the SRS unit has fired a bag or tensioner, the unit is locked and can not be reused.

The impact sensors and control unit use a metal ball and a spring for a switch. Once triggered, it is permanently triggered. Some people open them up and put everything back together, but that seems super sketchy.
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      09-12-2017, 04:29 PM   #9
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Quote:
Originally Posted by MightyMouseTech View Post
Was not sure about BMW, I know with Honda, once the SRS unit has fired a bag or tensioner, the unit is locked and can not be reused.

The impact sensors and control unit use a metal ball and a spring for a switch. Once triggered, it is permanently triggered. Some people open them up and put everything back together, but that seems super sketchy.
1000% SUPER sketchy!
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      09-27-2017, 09:15 AM   #10
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Quote:
Originally Posted by One28Goat View Post
Hey, I am replacing the steering wheel airbag on my 128i. It was in a front end collision and I want to make sure the bag doesn't deploy as soon as I connect it.

Does anyone know or have any guides or links? All I can find is takata recall articles. Or is this something I really shouldn't be worried about?
Did you replace the steering wheel airbag? Just wondering if you replaced the triggered sensor first?

I'm asking because previous owner of my 135i jumped a curb and triggered both curtain airbags/seat belt tensioner/battery safety terminal.

I've replaced the cheapest parts first just in case they deployed. Replaced seat belt tension, BST cable and they reset without any issues and didn't deploy after reset. There are no codes saying there are any issues with sensors. So if they didn't deploy after reset the sensor must not be triggered you would think. Am I correct on that as worried about installing the very expensive curtain airbags and have them trigger?

Last edited by carloverthepond; 09-27-2017 at 09:57 AM.
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      09-28-2017, 09:14 PM   #11
One28Goat
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I have replaced the seat belt and its pretensioner and they didn't go off again. I have an airbag but I haven't put it in yet so that's a good sign. I haven't replaced any triggered sensors. Some say that's risky others say its fine. I actually don't know where it (they?) are.
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      09-29-2017, 08:46 PM   #12
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I know where all the airbag sensors are but how would you know they are damaged or tripped? After all my car wasn't in a collision. Shouldn't a sensor show a trouble code if it needed replacing? An if they are tripped wouldn't the BST cable and seat belt tensioner I replaced have blown?
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      10-03-2017, 01:53 PM   #13
carloverthepond
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Installed both curtain airbags, BST and seatbelt tensioner - no issues with unexpected deployment! Cleared codes all working and no error codes.
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      10-03-2017, 04:14 PM   #14
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Quote:
Originally Posted by carloverthepond View Post
Installed both curtain airbags, BST and seatbelt tensioner - no issues with unexpected deployment! Cleared codes all working and no error codes.
Nice. I think I might just do a 2Ohm resistor for the side airbags and see how that works. At least for a while.
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