Seatbelt pre tensioner resistance too high

Mike Atkisson · 11-26-2021, 09:24 PM

I purchased a 2012 535i that had hit a pole. Had blown driver side knee airbag, steering wheel airbag, and a pillar airbag.

I replaced all 3 airbags from a donor car and still had 1 fault in the Airbag module. It was for seatbelt pre tensioner. I swapped the driver seat belt assy and the fault did not go away.

Donor car had a blown motor so all airbags we're good and assumed seatbelt should be good too.

Could the airbag module behind the glovebox cause the seatbelt error to not go away?
I need the fault to clear to be able to get car through inspection, so hoping it might be an easy fix.

M_Bimmer · 11-26-2021, 11:11 PM

Did you replace the belt or the buckle? (buckle = red release button)....

There is a pyro in the buckle portion that pulls your belt taught when in an accident...it's the tube labeled "Autoliv"...

Be careful, the buckles are different between pre-LCI vs LCI....and you need the pre-LCI version....

Unspec · 11-26-2021, 11:50 PM

Given that the seat belt buckles are directional, OP probably swapped the actual belt. OP, you need a new buckle.

Mike Atkisson · 11-27-2021, 12:55 PM

Thank you all for the information.

Looks like I need to go ahead and swap in the black seat.

Mike Atkisson · 11-28-2021, 05:52 PM

Swapped the driver side seat out of the donor 550i and got a new fault. Something about memory module...

So I swapped the module in the seat and no more Airbag light.

Thank you again for pointing me in the right direction. When looking at my old seat I could clearly see that the pre-tensioner on the buckle did it's job.

11-26-2021, 09:24 PM	#1
Mike Atkisson Private First Class 21 Rep 174 Posts Drives: BMW 540ix Join Date: Jun 2020 Location: Tucson, AZ iTrader: (0) Garage List 2014 BMW 435i [0.00]	Seatbelt pre tensioner resistance too high I purchased a 2012 535i that had hit a pole. Had blown driver side knee airbag, steering wheel airbag, and a pillar airbag. I replaced all 3 airbags from a donor car and still had 1 fault in the Airbag module. It was for seatbelt pre tensioner. I swapped the driver seat belt assy and the fault did not go away. Donor car had a blown motor so all airbags we're good and assumed seatbelt should be good too. Could the airbag module behind the glovebox cause the seatbelt error to not go away? I need the fault to clear to be able to get car through inspection, so hoping it might be an easy fix.
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11-26-2021, 11:11 PM	#2
M_Bimmer Captain 574 Rep 824 Posts Drives: G12 B7, G07 XB7, F02 B7, 991.1 Join Date: May 2020 Location: Left Coast iTrader: (0)	Did you replace the belt or the buckle? (buckle = red release button).... There is a pyro in the buckle portion that pulls your belt taught when in an accident...it's the tube labeled "Autoliv"... Be careful, the buckles are different between pre-LCI vs LCI....and you need the pre-LCI version.... Attached Images Last edited by M_Bimmer; 11-26-2021 at 11:16 PM..
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11-26-2021, 11:50 PM	#3
Unspec Colonel 1295 Rep 2,587 Posts Drives: 2015 BMW 535xi Join Date: Apr 2019 Location: DMV iTrader: (1)	Given that the seat belt buckles are directional, OP probably swapped the actual belt. OP, you need a new buckle. __________________ 2015 BMW 535xi Bootmod3 Stage 2 \| ER charge pipe \| ER Catted DP \| Remus Exhaust \| Gplus FMIC \| KW V3 \| Turner Monoball thrust arm bushings \| Wallet regrets ISTA VM Setup/Tutorial
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11-27-2021, 12:55 PM	#4
Mike Atkisson Private First Class 21 Rep 174 Posts Drives: BMW 540ix Join Date: Jun 2020 Location: Tucson, AZ iTrader: (0) Garage List 2014 BMW 435i [0.00]	Thank you all for the information. Looks like I need to go ahead and swap in the black seat.
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11-28-2021, 05:52 PM	#5
Mike Atkisson Private First Class 21 Rep 174 Posts Drives: BMW 540ix Join Date: Jun 2020 Location: Tucson, AZ iTrader: (0) Garage List 2014 BMW 435i [0.00]	Swapped the driver side seat out of the donor 550i and got a new fault. Something about memory module... So I swapped the module in the seat and no more Airbag light. Thank you again for pointing me in the right direction. When looking at my old seat I could clearly see that the pre-tensioner on the buckle did it's job.
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