seat occupancy code

[Henn28]

Looking for some lessons learned and advice on this issue. I've looked on this, and Bimmerforums but can't find anything conclusive that will point me in the right direction.

The seats that I picked up from fellow board member 5S0NG are finally reupholstered. Aside from the fact that this took way, way too long, I think I want to move into the car for good they are so comfortable. New foam on the bottoms, new leather bolsters and headrests, and new Uberkaro fabric from member Bimmerbreaker (ASC Fabrics) for the center sections.

The upholstery guy built up the center sections with extra batting which makes them super comfortable, I think the combo of leather and uberkaro looks great (my own version of the $4000 Porsche 911 "heritage" upholstery option), and man they are comfortable with the new lower foam and extra padding in the centers. Unfortunately, the leather bunches up a bit when the seat back articulates forward, and they could be a bit tighter in other places, but after 2 years I was just happy to have them back. The pic below is with the all functions of the seats adjusted full forward to help get to the rear bolts. The headrest, on the other hand, are way nicer than OE with new leather and electric adjustability. Super happy overall. I'd gotten used to the insanely poor shape my OE seats were in and can't believe how nice these feel. It really helps that the upper back is adjustable and the upholsterer put the steps in the uberkaro in the right places for support.

Heat is very nice too and works great. My OE seats didn't have heat, but I got the correct control panel off of ebay and the guy steamed pads off the old foam off and glued them onto the new foam.

Eventually my plan is to put the uberkaro in the centers of the rear seats too.



The swap was easy, except for the fact that I'm left with an airbag light on the dash which was initially for the seat belt tensioners and the Seat Occupancy detector. The tensioner codes reset with the foxwell, but the occupancy detector has not. After digging into it more today, it looks like the new seats don't have the same occupancy detector as the old ones. I believe the new ones are post LCI comfort seats, which on RealOEM show having the same basic mat and little box under the seat, but in reality the new ones I put in don't have this small box anywhere that I can see under the seat. So, I'm left to assume that 1) the mat has failed or 2) the module is looking for the small box and not finding it.

Old Seat with the plug to the small (black) box that is labeled "occupancy sensor " in real oem circled:


New seat with the spot circled where it should snap into, but simply isn't there. The arrows in both pics point to connectors that run into the seat, presumably to the occupancy detector mat and heat mat. They are unfortunately different between the old and new seats, making it impossible to simply plug the little box into the new seat wires:


If whatever module that controls this stuff is looking for this little box and cant find it, perhaps I could swap or splice in the one in from my old seat and install a resistor that is available on ebay to clear the code and airbag light by fooling the car into thinking the seat is occupied. Or, I read on the E39 forum that the airbag light and code for this problem can be switched off in INPA, Foxwell, etc.

I've messaged 5S0NG as I'd like to get the VIN that the seats came out of so I can figure out exactly which diagram to look at on RealOEM. Hopefully he's up on the board still.

Anyone have any experience with this issue?

[andrewwynn]

I think it's a little more tricky than resistor but most cars you can buy an ass detector simulator. That would be my go-to on having that problem.

You would have to be aware the airbag would likely deploy full force so you would want to never have small passenger in the front seat.

You would also have to either code out the seat belt warning or always buckle the seatbelt.

My wife's old e53 butt sensor would error when the cabin was below freezing and i was pretty sure I'd have to do the seat mat simulator route but we traded the car in first.

[Henn28]

Thanks Andrew. I"ve got to get smart on simple coding, now that I've got the full suite of BMW Tools up and running again on my laptop.

[Clavurion]

These are the related parameters with NCS on airbag module (MRS).

Passenger seat belt buckle:

GURTSCHLOSS_BEIFAHRER_1

GURTSCHLOSS_BEIFAHRER_2

Passenger seat occupancy sensor:

ERKENNUNG_SITZBELEGUNG_1 passenger seat occupation

ERKENNUNG_SITZBELEGUNG_2

SBE1_STATUS_VERZ_1

SBE1_STATUS_VERZ_2

SBE2_1 (this should already be not active)

SBE2_2 (this should already be not active)

[andrewwynn]

The coding would be for seatbelt alarm passenger side.

I often pack my travel bag on my passenger seat so i disabled the seat belt alert for my passenger seat (and set driver alert to 500m). If you use the seat mat simulator box it will tell the car somebody is always in the seat which has a couple issues: 1) seat belt alert when empty 2) airbag will deploy with no person and at full strength.

[Henn28]

I think I need to do a deep dive into where the mat is located in the bottom of the seat. Maybe it’s replaceable without tearing the leather off. Perhaps the foam and leather can be removed as one, and the mat then is accessible?

I also still can’t figure out why that little box is missing from the bottom of the new seat. Couldn’t hurt to see if it will plug into the wiring under the seat. The mat side plug though is completely different than the one on the small box.

[andrewwynn]

People have explored mat replacement and i think I've seen ten threads with only one success story which did involve reupholster.

I replaced my whole seat bottom for $50 but i think you said you replaced the whole seat with incompatible model.

You can look into if the pad just has a different connector and you can swap from old seat. Or: did somebody cut the lead from the seat mat?

Did you say the seats are replaced seats or reupholster? Too manyb threads on seats to keep track.

Look though the parts on realoem you might discover if the mat box is incorporated into the new seat or just was removed. Also: is there a chance parts were swapped? Do you have driver seat bottom on passenger side? Look under your driver seat for the butt sensor box.

[Clavurion]

Originally Posted by Henn28

I think I need to do a deep dive into where the mat is located in the bottom of the seat. Maybe it’s replaceable without tearing the leather off. Perhaps the foam and leather can be removed as one, and the mat then is accessible?

I also still can’t figure out why that little box is missing from the bottom of the new seat. Couldn’t hurt to see if it will plug into the wiring under the seat. The mat side plug though is completely different than the one on the small box.

The sensor mat is between leather and seat cushion. If reupholstering it would be advisable to renew the mat anyways.

[Henn28]

Originally Posted by Clavurion

The sensor mat is between leather and seat cushion. If reupholstering it would be advisable to renew the mat anyways.

Unfortunately they’ve just been reupholstered and I’m getting the code after swapping them in. I suspect my module is looking for the separate sensor that mounts under the seat and connects between the mat and the car. My car is a 2002 and the seats came from a 2006 (I believe). They don’t have this separate small box. Just ran an inpa sweep and came up with (thanks google translate):
112 seat occupancy determination
Error currently present
Line against plus
Error not sporadic

So yep, seems like the sensor pad is shorting.

Inpa also shows the “see built in” as “yes”. Which tells me the module is smart enough to see that the small box isn’t present on the model seal I swapped in, and it’s just reading a short in the mat.

[andrewwynn]

https://www.bimmerfest.com/threads/p...sensor.614533/

Some good reading.