Seat belt buckle contact driver: interruption

Hello,
i have airbag error icon on my instrumet cluster. So i connected BimmerLink and BimmerLink shows me this two errors (airbag in Error memory):

• Error code 9309C4
  Error description Seat belt buckle contact driver: interruption

• Error code 93097C
  Error description Driver side airbag: Resistance too great

any ideas? Could be these false errors, and its actually related to 12v battery? Car is 2015 and probably on original 12V battery. I don't have any other symptoms for 12V battery false.

Could be wiring under the driver's seat when vacuuming ?

Likely, not the 12v but would not hurt to be proactive and change that out first. Haven't seen the first error before - could be related to hitting the under-seat connections while cleaning - might check those are tight. The' Driver side airbag: Resistance too great' error has popped up for a few of us. Did on my 2015. I was once told that it was corrosion on the air bag connectors, but it appears it is tension on the air bag connection wires puling on the connectors, causing a slight change in the 'check' voltage that signals the car computer systems that the airbags are OK. Dealer replaced my steering wheel airbag when I had that error - car was still under the factory warranty at the time. Expensive job (around $2K) if they have to replace the air bag out of warranty. For a couple of hundred $, a BMW dealer can run full diagnostics and pin-point the cause. If the airbag needs replacing you might try calling BMW corporate to see if they will consider a 'good will' repair, since it is a known fault.

https://static.nhtsa.gov/odi/tsbs/2016/MC-10146965-9999.pdf

https://youtu.be/k147sRXYuJQ
Wiring under the driver's seat was disconnected. BimmerLink can clean airbag errors now.
Ticket closed

Anyone else had the 9309C4 code? It comes up regardless of the seat belt use. I unplugged and reseated the yellow connector under the seat to no avail. Does anyone have the schematics?

gt1 said:

Anyone else had the 9309C4 code? It comes up regardless of the seat belt use. I unplugged and reseated the yellow connector under the seat to no avail. Does anyone have the schematics?

Click to expand...

Error code 9309C4
Error description: Seat belt buckle contact driver: interruption

"Driver's seat belt buckle contact

The driver's seat belt buckle contact is integrated into the seat belt buckle on the driver's seat. With help of the signal from the driver's seat belt buckle contact, the Crash Safety Module (ACSM) detects whether the driver's seat belt is fastened or not. ACSM stands for ”Advanced Crash Safety Module”, referred to as the "Crash Safety Module".

The seat belt warning light (visual seat belt warning) in the instrument cluster lights up from terminal 15.

Once the driver's seat belt has been fastened, the visual seat belt warning disappears. The acoustic seat belt warning is switched off. The output of the visual and acoustic seat belt warning is dependent on the national-market vehicle."

If you haven't disabled the seat belt warnings, buckling the driver's seat belt should result in the visual and acoustic warnings disappearing. If this doesn't happen, the driver's seat belt buckle contact might not be working (a Hall effect sensor detects the male part of the buckle when it has been inserted into the female part). This contact is in the buckle. It passes more current when the buckle is buckled and less current when it isn't which is how the ACSM knows whether the seat belt is buckled. However, if it passes no current (i.e., current is interrupted), I'm guessing that error code 9309C4 would be stored. The yellow plug under the seat passes this seat belt buckle current, but you've eliminated this plug as the source of the problem.

Art, thanks. Good to know it is a Hall effect sensor, not a mechanical switch. I remembered that I coded the set belt reminders not so long ago. I coded it back, will see, maybe it caused the code to pop up.

gt1 said:

I remembered that I coded the set belt reminders not so long ago. I coded it back, will see, maybe it caused the code to pop up.

Click to expand...

For what it's worth, I eliminated the visual and audible seat belt reminders via coding quite a while ago and have never seen this error code. I believe these were standard mode BimmerCode options, so I didn't have to muck around in expert mode where I might have screwed something up.

One other reason for coding it back was to see if it buckling up would turn off the seatbelt light on the dashboard. Turned out, it still works like it should- I buckle up, the light and chime stop. So it seems that there is nothing wrong with the entire buckle circuit. Coding with Bimmercode clears the error codes, so the airbag warning disappeared. But it returned later the same day. At this point, I'm out of ideas for troubleshooting. Maybe the buckle switch is robust and has a back up circuit, and only one out of two failed? I can't check it without the schematics. Maybe my 12V battery is starting to fail and ACSM is the most sensitive module? If this was the case, the same code would be mentioned here quite a lot.

I removed the seat to check the seat belt buckle circuit. The cable from the buckle has two wires, it terminates at the white insert of the underseat connector.



While handling the connector I pulled the cable ever so slightly, and one of the wires fell apart.



I removed the insert, extracted the pin, and soldered the wire together. Noticed that the other wire also had a nick on it, but the wire was still strong.



I reassembled the connector and took some measurements between the buckle wires. The ohmmeter indicated an open circuit regardless of the seatbelt insertion. Thanks to @alohart I wasn't surprised, it was expected for the Hall sensor. Plugged the yellow connectors together and measured the voltage. It was a bit over 0.7V without the seatbelt, and under 0.6V with it. Not much of a difference, but this is normal, as confirmed by the seatbelt light on the dashboard. I reinstalled the seat and cleared the airbag code. It's been 3 days and the code hasn't come back. When I tried to reset the code before, it returned on a second ignition cycle. This assembly defect has to be rare or unique, it explains why I couldn't find much relevant info online. What is puzzling is that the seatbelt indicator worked normally even before I fixed the wire. I hope that my bragging here is not premature.

Nice to see posts like these!

BMW i was BORN ELECTRIC back in late 2013 and we know how BMW lost their EV way over the past ten years.

How could we be excited today by a 5,300 lb. iX SUV or a ICE-platformed i4 that keeps its transmission tunnel in the all-electric powertrain model?

I'm just happy to see members here tweaking with their i3s and keeping them on the road versus turning them in for some dumb VAG EV:
https://www.carmagazine.co.uk/electric/volkswagen/

In my case it was a broken wire under the driver seat.

i9998217 said:

In my case it was a broken wire under the driver seat.

Click to expand...

Welcome to the forum i9998217!

Any thoughts from you (also you, gt1), why those wires might have failed?

Seat belt sensing tech is something that BMW should have solved long ago.