Passenger Airbag Logic

[heinzboehmer]

Anyone know what conditions have to be met for the passenger airbag to go off? Do the occupancy sensor and belt buckle sensor both have to be active? Just the occupancy? Just the buckle?

I was messing around with INPA today and realized that my passenger occupancy sensor was not sensing if there was someone in the seat. It always reported the seat as empty. If this sensor is required for the airbag to go off, then my failed sensor could have been incredibly dangerous for a passenger. I'm surprised that the sensor was engineered so that its failure mode means reporting an empty seat. Maybe INPA was reading it wrong?

Regardless, I went in and disabled this sensor in the airbag module just in case I ever get into an accident with a passenger. Now all airbags should go off whenever the driver ones do. Makes for more expensive crashes, but also less dead passengers.

[eacmen]

Anyone know what conditions have to be met for the passenger airbag to go off? Do the occupancy sensor and belt buckle sensor both have to be active? Just the occupancy? Just the buckle?

I was messing around with INPA today and realized that my passenger occupancy sensor was not sensing if there was someone in the seat. It always reported the seat as empty. If this sensor is required for the airbag to go off, then my failed sensor could have been incredibly dangerous for a passenger. I'm surprised that the sensor was engineered so that its failure mode means reporting an empty seat. Maybe INPA was reading it wrong?

Regardless, I went in and disabled this sensor in the airbag module just in case I ever get into an accident with a passenger. Now all airbags should go off whenever the driver ones do. Makes for more expensive crashes, but also less dead passengers.

FWIW I went 120mph into a tire wall on track with supposedly functioning airbags and none of the airbags deployed. I did not have an airbag MIL light or anything. Even had the recall done.

I haven't been able to find any documention as to what criteria need to be met for the airbag to deploy. If you find it please send it my way. Every expert that has seen the car has said the airbags definitely should have gone off.

I wasnt aware our cars even had a passenger occupancy sensor.


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[Redline]

FWIW I went 120mph into a tire wall on track with supposedly functioning airbags and none of the airbags deployed. I did not have an airbag MIL light or anything. Even had the recall done.

I haven't been able to find any documention as to what criteria need to be met for the airbag to deploy. If you find it please send it my way. Every expert that has seen the car has said the airbags definitely should have gone off.

I wasnt aware our cars even had a passenger occupancy sensor.


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Speed of deceleration, tire wall slowed you enough to not warrant deployment.

[eacmen]

Speed of deceleration, tire wall slowed you enough to not warrant deployment.

The deformed strut towers, totaled frame/subframe damage, and my injured hip disagree with this. I've seen much less serious wrecks where the airbags went off.


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[heinzboehmer]

I'm glad you came out okay from that eacmen. I remember a thread on M3Forum that had pictures of a high speed crash on track where the strut brace had folded up like a pretzel, was that you?


Also, I think I might have been too harsh on the BMW engineers. A bit more research told me that a broken occupancy sensor will result in an airbag light and presumably will cause the car to assume there's someone in the seat.

After coding out the sensor, I got a light on the dash and a code saying something about that sensor. Turns out the airbag module doesn't like it when it's seeing readings from the sensor but is not expecting them. So I went under the seat to unplug it and found this:



The sensor must have failed in the past and someone installed this to get rid of the light. They must have also messed something up because their sketchy homebrew sensor emulator thing was reporting that the seat was empty. Anyway, removed that thing along with the occupancy sensor module and now my car is happy and won't try to kill my passengers.

[eacmen]

I'm glad you came out okay from that eacmen. I remember a thread on M3Forum that had pictures of a high speed crash on track where the strut brace had folded up like a pretzel, was that you?


Also, I think I might have been too harsh on the BMW engineers. A bit more research told me that a broken occupancy sensor will result in an airbag light and presumably will cause the car to assume there's someone in the seat.

After coding out the sensor, I got a light on the dash and a code saying something about that sensor. Turns out the airbag module doesn't like it when it's seeing readings from the sensor but is not expecting them. So I went under the seat to unplug it and found this:



The sensor must have failed in the past and someone installed this to get rid of the light. They must have also messed something up because their sketchy homebrew sensor emulator thing was reporting that the seat was empty. Anyway, removed that thing along with the occupancy sensor module and now my car is happy and won't try to kill my passengers.

Yup that was me. Still recovering tbh. Last track event was still about 10s slower than my previous times.

Glad you found the issue! Aren't previous owners the worst?

[heinzboehmer]

Yup that was me. Still recovering tbh. Last track event was still about 10s slower than my previous times.

Glad you found the issue! Aren't previous owners the worst?

Yeah that accident looked quite intense. Wish you the best! And agreed!