BMW E36 1996 - Airbag Light (Pretensioner) - Help Needed

[Sin Of Greed]

Hi All,

I've recently had an airbag light popup and I'm hoping someone on here has some more knowledge of the SRS systems on a 1996 or older E36.

I have a B800 scanner and also INPA both reporting the same code for the Passenger Side Pretensioner. Or more specifically, code 17 from INPA:

17 Analoge Gurtschlossabfrage Beifahrer
Rough Translation: 17 Analog passenger seat belt buckle query

I have the "old style" non hall-effect mechanical pretensioners: (PART: 72118167711) As far as I can tell, these have zero wires coming off them. I have also removed the passenger seat and there are 0 wires connecting it to the car and poking through the floor / dangling. From what I can see under the drivers seat, it's the same scenario with 0 wires.

This is what the pretensioner looks like for early '97 backwards:



Here's a screenshot of the airbag status screen on INPA, which appears to show my car only has a drivers side airbag (Steering wheel) and no seatbelt pretensioner connections or passenger mat sensor:


I'm willing to purchase and fit a new pretensioner, but the question remains, if there are no wires - How on earth does the SRS / MRS module know about the pretensioner being faulty and is giving me a direct code for the passenger side?

[RUSSELLM]

I can see the picture of the buckle.

But I presume the pretensioner is on the belt ?

[anonymous-user]

This may be of help:

https://www.steerbythrottle.com/hccyong/forum/SRSL...

[Sin Of Greed]

Island Hermit said:

This may be of help:

https://www.steerbythrottle.com/hccyong/forum/SRSL...

Cheers for the link. I have read this before and is what led me to further confusion. As it mentions failure of the switch inside the pretensioner which will trigger the code. I completely understand this, but surely I need a wire from the pretensioner that runs to the ZAE / SRS module for it know the switch has failed... As mentioned, looking at mine, there are no wires and neither do the ones I can see online / eBay!

I just don't understand how the ZAE / SRS module would be able to communicate with switch to know it's faulty!

[Sin Of Greed]

RUSSELLM said:

I can see the picture of the buckle.

But I presume the pretensioner is on the belt ?

Pretensioner is part of the buckle housing. Mechanical wire under slight load gets tugged in the event of an accident which retracts the buckle by a few inches, thus pulling the seatbelt down. Not sure if these early E36s have dual pretensioners with ones on the belt. All the codes are pointing to the pretensioner / buckle housing having a fit (Link above posted by another member shows the technical document for why they fail; small microswitch degrades over time causing a circuit break). This just confuses me more, because there are no wires whatsoever that could tell the ZAE / SRS system that there is a circuit break!