Seat occupancy sensor simulators.

[YosDad]

Vinci, Dewaye sent me a link to your thread, my situation is about an 06 MINI Cooper S.

My seat occupancy switch does not work and causes the AB red light to stay on.

I do not care about any plug that fits my under seat connectors, I just want to unplug the bad seat switch and wire in the appropriate resistor package to emulate a seat switch with a person in the seat.

Of course we must assume that the MINI uses the same system as the Z3 (maybe, maybe not), but if it does not, no harm.

Back in one of your responses you gave the resistance values of the resistors you were using. Can I simply install a resistor across the wires going to the seat switch and achieve my desired result.

Thank you for all your research and experimentation to help everyone with similar problems.

If you think this will work I would be happy to purchase a module from you and make it fit.

thanks

YD

[bully9au]

I did the weigth check on the pad, as I just did seats in the coupe.
Here is what I found
the pad in the seat is 1.5 meg ohms with no occupant
with me in the seat 9K ohms (Im about 185lb)

I tried sevaral different circuits (as I had a SRS tool for rests).
1.) I tried the one vince uses (2) 100K ohm resistors with the diode
the light is indeed out

2.) I tried one with a 10k ohm and diode so it would think I was in the seat
no light so "it worked"

3.) I tried one with a 1.5 meg ohm and diode.
Light was out so "it worked"

The question really is what would happen IF???
Would the bag deploy?
Would it NOT deploy since the pass seat belt is not done (no passenger).
If the seat belt is in (passenger) would it deploy?

Really what no one seems to know 100% is the complete circuit and operation of the system. i.e. with simulator, belt, and no belt. What is the function.

personally I went with the 10k ohm and diode to simulate a person in the seat.
Based on my measurements of the pad in my seat.
Also I imagine that since the belt would not be in if no passenger occupant the bag would not deploy.

Note: When measuring the seat I found no directional characteristics, such as a diode.
The circuit for me would not work with out the diode (i.e. just resistors).

This is just information I found with regard to my car and for my personal use.

Maybe the following is help with your What If:


The SOMS consists of a polymer sandwich with integrated sensors whose resistance values change proportionally with applied force. The sensor mat layout is tailored to each individual seat design. Due to this flexibility of design, the sensor matrix may be mounted in three different ways: 1. Between the seat foam and the seat cover; 2. Between two layers of foam; and 3. Between the shell of the seat and the foam. Sensor resistance is measured electronically. The signal "passenger seat unoccupied" is obtained and the airbag-ignition-circuit is switched off only when the sensor resistance lies between two pre-defined values. Outside of these two values, and this does include if the system is damaged, the seat is always considered occupied and the airbag-ignition-circuit remains "on standby".

[YosDad]

bully9au, thanks for your reply. What you say means that if the seat sensor fails, it will fail in a "gonna fire the AB" mode. The red light may be on, but the AB will fire if an accident occurs?

The my problem is just getting the red light to go away?

Do I understand you correctly, or do I need to experimentally install resistors until I find a value that turns the light out?

thanks

YD

[dwaynemosley]

While having a brainstorm, I took the removed seat apart, removed the occupancy mat, installed it inside the seatback of the new seat and connected it to the harness. My thinking here was that without pressure on the mat, I would eliminate the airbag and "passenger airbag off" light. This worked, but the minute I connected the passenger side seatbelt, the "passenger airbag off" light illuminated and I'm back to square one.

I rearranged it behind the top cushion, it went out again, but the minute I sat in the seat leaned back against the seat back, the light illuminated. Curses.

I'm stumped. Any suggested workaround is very welcome.

[bully9au]

bully9au, thanks for your reply. What you say means that if the seat sensor fails, it will fail in a "gonna fire the AB" mode. The red light may be on, but the AB will fire if an accident occurs?

The my problem is just getting the red light to go away?

Do I understand you correctly, or do I need to experimentally install resistors until I find a value that turns the light out?

thanks

YD

That SOMS quote came from a BMW engineer. My understanding of what he says is that 1. sensor between 2 values = unoccupied seat airbag Off. 2. sensor outside these 2 values = occupied airbag ON.
3. sensor damaged = unoccupied airbag off.

I don't recall reading anywhere here what exactly Vinci's and others bypass does. They have said it "tricks" the system into believing the SOMS is in place and it certainly works ( I plan on getting one from Vinci soon). However I would like to know is it tricking system into thinking seat occupied or unoccupied. Anyone know???

[Vinci]

I am pretty certain that the simulator just provides a resistance that is within the range that the sensor is looking for. Nothing more. It is a fairly simple system, so there isn't much to the "trick".

[TRspitfire]

Was just browsing German ebay and here is a guy selling simulators:

http://cgi.ebay.de/BMW-Airbag-Sitzbe...3%3A1|294%3A50

[Vinci]

I don't know why they didn't make theirs smaller. There isn't that much to it. They also cover up the release tab on the plug.

[YosDad]

One more question.

If you successfully fool the system into believing that a person is in the passenger seat, will the system now want the seat belt buckled to keep the seat belt warning turned off?

YD

[Vinci]

I ran my car for a week or so with a simulator in place and no passengers before I shipped the first one. I did not have any warning lights. I don't imagine later models would be any different.

[LAWLence]

Has anyone figured anything out for the dual stage airbag yet?

[ckm]

Vince,

Are you still making these? I could use one as I am looking to replace my stock seats.

Chris.

[Vinci]

Sorry, Chris. I am not making these anymore. They were too much hassle for what I was charging and I had too many people stiff me on the bill.

The circuit has been posted in several threads and isn't difficult to make.

[ckm]

Thanks, found the diagram, I was just trying to save some time.

Chris.

[dome2degas]

I need help finding a solution to my broken occupancy seat sensor in my 2005 Mini Cooper S. (Dealership wants over $1100 for the repair.) I just want to bypass the seat sensor so that my passenger airbag works and the annoying red light disappears from my dash. Thanks! (PS. I know nothing about electricity or building circuits.)

[ckm]

BTW, put up a how to make these here http://forums.bimmerforums.com/forum....php?t=1623360

[peteyang12]

Thanks for all the helpful information in this thread.

I have made several seat occupancy sensor simulators using OEM BMW plugs and parts (4k7 resistor in parallel with a 1N4005 diode) that work perfectly to turn off the passenger SRS warning light on my E46 after clearing the code.