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Discussion Starter #1 (Edited)
I pulled an SRS code off my M5 the other day and it was saying the passenger pretensioner is faulty. To my understanding, that's this part here:

https://www.fcpeuro.com/products/bmw-seat-belt-tensioner-front-left-lower-genuine-72118257797

So, my question is this (to anyone that might know): What exactly is it that goes bad with the pretensioner? Is it a sensor or something inside the unit that goes bad? If so, is this something that's repairable by opening it up and fixing the circuitry or is it just completely toast?

I am tempted to buy a used one off eBay but I feel like that's a gamble buying a used one when they could just as easily be bad as well.

Let me know your guys thoughts! Seems like anything electrical could be easily be rebuilt, maybe that's not the case with this though?

FYI, the car has never been in an accident so I don't have a pretensioner that actually blew up on impact or anything.
 

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Yeah, WDS has an alert about the wiring. The fact that you are getting a code means that the MSR module has detected an electrical problem in the pretensioner wiring or the igniter in the pretensioner.

Seat belt tensioner WDS alert.JPG

Seat belt tensioner.JPG
 

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Discussion Starter #4
So it sounds like it's just the wiring then. I took the seat out of the car and inspected the pretensioner. The charge has not gone off so I know it wasn't the result of an accident or anything which leads me to believe it's likely the wiring.

From what I'm reading online that wouldn't be all that uncommon since they sell replacement wiring and other people have had the issue.
 

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What are you using to read the code? I had something similar...

I used a handy little hand held reader which gave a table and then an offset, resulting in a passenger pre-tensioner error (supposedly).

I tried a different pre-tensioner and different sections of wring, removing the seat and finally the airbag ecu etc. After a few hours I thought all was well and put everything back.

Later on, the light came back on!!!! This time I used the GT1 to read the code and it pointed me to the door airbag circuit. Popped the door panel off and stripped/cleaned the airbag connector, all has been well and good since (not sure what was up with it, all seemed clean and good).

Might be worth it to have it read with a GT1 just to be safe, there are a few with it now.

If you used this to read it, then go after the pre-tensioner :)
 

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Discussion Starter #6
I used the Peake airbag tool to diagnose it and it gave me the code for faulty pretensioner.

I just put in new seats today and the door panels are coming off tomorrow so I'll see if there's any connections that need to be cleaned.

I wish I had a GT1 or something better but right now I don't. I am working on getting everything setup on my laptop so I'll have access to NCS Expert and everything else.
 
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