Arg- two BMW's with airbag light on

[ThreeGermans]

Ok, I am new to this issue (I have several other cars, none of them have had this problem.. yet) so please go easy on me. I basically have two questions:

1) Can I disable the passenger seat-sensor related lights/warnings (because I don't want to run into issues with yearly vehicle inspection, which is mandatory in my state. and because it's annoying to drive around with the 'seat belt warning' dinging constantly) WITHOUT negatively affecting occupant crash safety?

2) What do I need to read in order to start learning about coding and changing stuff on my BMWs (INPA, ISTA, Bimmercode, Carly... I only have a vague notion that the first 2 are official BMW/dealership tools and the 2nd two are aftermarket)?


First question:

I have an E53 X5 (and an E85 Z4), both of which seem to have issues with the passenger seat occupancy sensors. On the X5, it will randomly decide that someone is in the passenger seat (it is almost always empty) and so therefore it needs to remind the non-existing occupant to wear their seatbelt. It does this by playing a chime loudly and repeatedly. This is rather infuriating. It always happens when I've accidentally placed something on the seat like my laptop bag, but will sometimes happen when I place something much lighter on the seat. I can sometimes get the seat sensor to 'reset' by punching the seat (yes, this is my stupid workaround. I don't expect it will last very long considering what I know about the sensor mat). Luckily, I am driving alone, with no passengers most of the time, so there is nobody there to witness this. I have clipped the seatbelt closed on the passenger side, which is another temporary fix, but I want to do something more proactive.

In the Z4, the sensor must have decided that there is a passenger in the seat who is too light weight to enable the airbags, however, it seems to be stuck on that mode, because even with a full-sized adult in the passenger seat, the "Passenger airbag off" light is on all the time regardless if nobody is in the seat or with an adult passenger in the seat. I suppose that this could be an airbag issue unrelated to the seat sensor, but the prior owner stated that the problem was with the seat sensor. For some reason, the seatbelt reminder chime is not activated, but the "Airbag" warning light on the dash is on. I am worried about passing inspection this way.

What are my options? I read that one can simply unplug the sensor in the seat. What does this do, exactly?

I assume that the airbags work according to the following algorithm, but I have done no research on this, and would like to learn/confirm:

-With nobody in the seat, or with a very light object such as a hat or keychain, the weight sensor sees 'zero' weight and will not remind the passenger to wear their seatbelt. (Passenger airbag remains off, but the "passenger airbag off" light is NOT illuminated because there is no hazard; nobody is in the passenger seat so there's no need to warn you that the passenger airbag won't deploy).

-With a small amount of weight in the seat (for example, a baby in a carseat, or a small child) the car will remind the passenger to wear their seatbelt if it is not detected as being closed/connected. However, it will light up the Passenger Airbag Off light as a reminder that the airbag will not deploy (or will deploy with less 'power'?) (The Z4 seems stuck in this mode. Somehow, the X5 seems to avoid this particular issue). This is to avoid injury from airbags to babies and children.

-With a 'full-sized adult' in the seat, the car will remind the passenger to click their seatbelt, and the "Passenger airbag off" light will go out. The airbag will fully deploy in an accident.


What are my options?

A) Address the seat sensor. From what I have read, repairing/replacing the seat sensor is expensive and difficult. These cars are >20 years old and it is cost prohibitive to spend much time and effort (I'm not sure if parts are still available). If this is inaccurate, feel free to let me know.

B) Just unplug the connector?
-Where do I find the connector, and what does it look like?)
-What happens if I do this? Does the car think there is NO occupant in the passenger seat? That's good because it will not remind an empty seat to put on their seatbelt, but it's bad in the rare case when I have a passenger; both because they won't be reminded to put their seatbelt on, but worse yet because the airbag won't activate in an accident? Or will it?

C) Can I 'code out' this problem or otherwise change the behavior/logic behind it? If so, I guess I will lose the ability to remind the passenger to wear their seatbelt. I am actually not too concerned with this because my children are all grown and we never have kids in the car. I would be a little concerned if I ever sell the car (probably will drive it into the ground, but need to think about all possibilities), but if I can undo the coding, that would be OK (I want to be honest with a future buyer, if there is one). And again-if I do this, what mode is the airbag in? Can I 'code' it to be always on as if there's always an adult in the passenger seat? That would be the safest choice for my situation.

Second question (and perhaps this should be a second post):
Where/how can I learn about coding different features/options in BMW cars? I have no idea where to start. I found a copy of INPA online and managed to install it, but I have no idea what to do with it. I'd love pointers to any starter/learning information to begin with.

Thank you

[andrewwynn]

Often it's the butt sensor and you can confirm with a decent scanner. Once confirmed, obtain a sensor simulator and plug that in.

It will think a person is sitting always so you need to ether code our belt warning or leave the belt buckled.

Any other feedback like error goes away when car is warm comes back when cold ?


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[X5chemist]

Mine has a passenger side simulator. Use a belt extender to by pass the ding ding. The extender works great.

Seat emulator. I have look up where I bought mine. The air bag will deploy with or without a passenger. Better to have a deployable air bag than not.

The two parts fixed my SRS 71 code.

[andrewwynn]

that seatbelt extender is clever that would work perfectly


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[ThreeGermans]

Thanks for the replies. I will do a deeper dive with the code scanner but no standard OBD2 codes right now. I will have to observe if the errors change when cold vs warm but I don't think so.

You can pass inspection with a buckle stuck in the seatbelt latch? Is it because they don't really look?

[andrewwynn]

They should not care the buckle is latched. The system will pass OBD2.

The cold/hot query relates to that the module itself will fail internally you will get a different error that you can't clear.

You need a proper scanner foxwell nt-510 or equivalent minimum.


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