Airbag circuit fault - passenger seat sensor

**Heeltoe** · 12-12-2006, 06:41 PM

After hauling an oversize passenger in my 1999 323is E36, the airbag fault indicator light came on. Had the code read at a local garage and it was "passenger seat occupant sensor". Reset the fault and all was OK until I again had another rider. Light came on again.
I have the dealer-supplied Bentley manual and, unless I'm missing something (entirely possible), the occupant sensor is not mentioned or shown in the pictorial diagrams or schematics. WTF? Has anybody ever replaced one of these? Difficult?

**JBURGS47** · 12-12-2006, 07:19 PM

i'd also like to know...

**dieseldriver99** · 12-12-2006, 07:23 PM

Common problem so it seems on E36's. Dealer told me that it was the seat belt control module. So I ordered one cheap on Ebay for $30. I also ordered the Bentley on BimmerZone.com for $50.95. I'm changing the module out this weekend. Otherwise, the Airbag bulb is getting removed.

"Doesn't got time for the pain..."

**laserdude** · 12-12-2006, 07:58 PM

Originally Posted by dieseldriver99

Common problem so it seems on E36's. Dealer told me that it was the seat belt control module. So I ordered one cheap on Ebay for $30. I also ordered the Bentley on BimmerZone.com for $50.95. I'm changing the module out this weekend. Otherwise, the Airbag bulb is getting removed.

"Doesn't got time for the pain..."

did you just get lucky? I searched ebay and could'nt come up with a "seat belt control module". What search parameters did you use? or do you have a link? My lights gone on a couple of times - I have the reset tool but I don't want to have to keep resetting.

**dlight26** · 12-12-2006, 08:06 PM

if you take out the airbag light it stills glows a faint orange color at night. I cant figure out y tho. There must be another bulb or something idk.

**NguyenHuu** · 12-12-2006, 09:46 PM

Originally Posted by dlight26

if you take out the airbag light it stills glows a faint orange color at night. I cant figure out y tho. There must be another bulb or something idk.

that faint glow is just light from your other bulbs that are also on at night and it's "leaking" through.

**dieseldriver99** · 12-13-2006, 07:08 AM

Ahh, yes, I already took care of that, I cut a round electrical tape and cover the hole. No half &^( job here okay!

Originally Posted by dlight26

if you take out the airbag light it stills glows a faint orange color at night. I cant figure out y tho. There must be another bulb or something idk.

**Heeltoe** · 12-13-2006, 01:17 PM

The local $tealership told me it was some sort of little mat that tucks into the seat cushion somewhere. Not very expensive, but the labor to replace it was ridiculous - seat removal, seat cover removal, etc, etc... $300-$400 range. Electrical tape on the bulb is looking better all the time, BUT with this fault in the system, what happens during an accident? Airbag deployment or not?

**dieseldriver99** · 12-13-2006, 01:21 PM

I've been told that it will work. So I am not taking any chances, I am replacing whatever needs replacing through FleaBay, yay!

Originally Posted by Heeltoe

The local $tealership told me it was some sort of little mat that tucks into the seat cushion somewhere. Not very expensive, but the labor to replace it was ridiculous - seat removal, seat cover removal, etc, etc... $300-$400 range. Electrical tape on the bulb is looking better all the time, BUT with this fault in the system, what happens during an accident? Airbag deployment or not?

**Heeltoe** · 12-13-2006, 03:23 PM

What kind of tool are you using to clear the fault?

**dieseldriver99** · 12-13-2006, 03:32 PM

I was just thinking of replacing the module, and find someone with OBD-II tools to reset it. I am not going to the dealer...

Originally Posted by Heeltoe

What kind of tool are you using to clear the fault?

**rizzag** · 12-13-2006, 03:51 PM

i have heard that if the light is on, NO airbag deployment in an accident. i had this same issue and somewhere on the net there was a DIY to make a little circuit board to trick the computer into thinking someone is sitting in the seat. i built it and reset the light and now all is well.

**rizzag** · 12-13-2006, 03:54 PM

found it!

http://www.apexcone.com/JimPowellHom...s/Recaros.html

**Heeltoe** · 12-13-2006, 04:28 PM

Sweet deal! Thanks. I can do that. This beats the pi$$ out of giving the $tealership enough money to pay for a semester at Harvard.

**Heeltoe** · 12-13-2006, 04:34 PM

BTW, why doesn't this little resistive mat show up in the Bentley manual as part of the airbag system?? My 99 323is coupe was the end of the road for E36. My Bentley manual states that it is for 92-98. Was this little mat new for 99 and therefore not documented? Anybody have an actual bmw schematic showing the resistive mat?

**dieseldriver99** · 12-14-2006, 07:07 AM

I will get this fixed. But how would one be 100% sure, even with the AirBag light off, that the passenger bag will deploy? If the car is about 10 years old, we could never be sure. Is there a way to test it without deploying it?

Originally Posted by rizzag

i have heard that if the light is on, NO airbag deployment in an accident. i had this same issue and somewhere on the net there was a DIY to make a little circuit board to trick the computer into thinking someone is sitting in the seat. i built it and reset the light and now all is well.

**Heeltoe** · 12-14-2006, 12:33 PM

Every time the car is turned on, the airbag system (and all other computer-controlled systems) performs a self-test. The airbag light comes on during this test. At the end of the self-test (4-6 seconds), the light goes out. If there is no fault found, the light stays off. If a fault is found (during this self-test or any previous self-test), the light comes back on and stays on until the fault is cleared. During the test, the igniters in the explosive charges are tested for presence - not enough current to set off the charge, just enough current to let the system know that the igniter is intact. If an explosive cannister was taken out of the system before running the self-test, the self test would fail. The only component not system tested is the explosive material itself. I work with a guy that actually worked for a company (now out of business) that made airbag explosive cannisters. The explosive is extremely stable and remains viable for at least 20 years.

Anybody have an E36 schematic showing the passenger seat occupant sensor (resistive mat) that is in the seat cushion?

**kvangenechten** · 12-14-2006, 01:24 PM

By the way you if you remove the bulb in the cluster for the air bag there is another bulb on the board. NOT easy to remove for the reason that someone may take the bulb out or it burns out. Extra little safty thing BMW put there to make our lifes easier.

**islandbimmer** · 12-14-2006, 03:00 PM

Not that hard but time consuming, no wonder these fail, it is under the seat cushion. It has a number of pressure sensitive contact points. I also have a reset toll for the SRS will possibly rent it out.

**LmtdSlip** · 06-07-2008, 10:54 AM

What about diagnosing a Pre-OBDII car?

**Black Isis** · 06-07-2008, 11:22 AM

if anybody was wondering i'm pretty sure this is the BMW part number for it 65778367599 search it on pelican parts and you will find it also on real oem.com

**mjcari** · 06-07-2008, 11:45 AM

I replaced this in my 1998 w/ sport seats. There is an updated design, and it required new seat foam too (not necessary IMO now that I replaced it) It was like $87 and it took me an hour. Remove the seat, leather, cushion, & replace. Also get the snap on connectors that hold the foam down to repalce the ones you have to break to get it apart.

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