Airbag light on. MOT imminent…

[ZedEyez]

First a confession. I’ve bought another Z3. Another cheap doer upper. 2.8 1998. I need to join Z3 anonymous if it exists.

I have the airbag light on… sometimes it’s very dim, sometimes bright but it’s on.

MOT is imminent. Scanned today with B800 and numerous codes showed:

Before clearing codes:
21 sensor, side airbag, right, line fault
20 sensor, side airbag, left, line fault
12 sensor, side airbag, left, data line
6 firing circuit , belt tensioner, passenger side
18 seat occupancy detector, passenger

Codes cleared, drove around the block, codes showing:

21 sensor, side airbag, right, line fault
20 sensor, side airbag, left, line fault
6 firing circuit , belt tensioner, passenger side

I guess I will need to remove the door cards and trace the side airbag wires/connectors. Is the belt tensioner the seatbelt connector? Does anybody have experience of dealing with these codes?

Thanks

 

[colb]

The tensioner is the seatbelt connector unit, it has a explosive charge in it that fires and tensions the belt when an accident occurs, its not servicable so if its gone bad a replacement will be required. Worth checking the wiring under the seat for loose or dirty connections before condeming the unit. The side airbag codes for right and left seem suspicious being both sides coding at the same time, might be worth checking the connector on the actual airbag module behind the glovebox for bad connections before pulling the door cards off to check that end. You should be able to source a good tensioner from breakers, try @spurs fan in a coupe or Quarry Motors online

 

[spurs fan in a coupe]

If you do need seat belt tensioner(s) I have a few.

 

[ZedEyez]

The tensioner is the seatbelt connector unit, it has a explosive charge in it that fires and tensions the belt when an accident occurs, its not servicable so if its gone bad a replacement will be required. Worth checking the wiring under the seat for loose or dirty connections before condeming the unit. The side airbag codes for right and left seem suspicious being both sides coding at the same time, might be worth checking the connector on the actual airbag module behind the glovebox for bad connections before pulling the door cards off to check that end. You should be able to source a good tensioner from breakers, try @spurs fan in a coupe or Quarry Motors online

Thanks for the advice. Should I disconnect the battery before checking for loose connections?

 

[colb]

Always best to disconnect battery when messing with airbags and once disconnected leave it for 10 - 15 mins before checking out the wiring connections.

 

[ZedEyez]

Got the glove box off. Whereabouts is the airbag module located? Thanks

 

[colb]

Seems I may have led you to the wrong location, its probably under the centre console forward of the gear stick, found a thread here

Airbag Control Module - zroadster.net

 

[colb]

Once you find the module check the connection pins are clean and wiring intact, to check the lines to the side airbag sensors you are probably going to have to access behind the door cards to check continuity of those wires with a test meter back to the module plug, don't have a pin out diagram but you may find one on internet or a bmw wiring diagram, anyone got a link to pin outs or wiring diagrams?

 

[ZedEyez]

So I took the passenger seat out. Fairly easy job. Then I hunted for the airbag sensors below the carpet thinking they may have corroded/failed somehow. I have been greeted with VERY soggy wet foam under the carpet…
Just checked the drivers side and super wet under drivers side carpet also

 

[mrscalex]

The crash detection sensors live under the carpet. They will give very different errors and based on that list are not a problem. However if they are swimming in water they may become a problem later.

The airbag module is next to the gear-lever under the carpet. It’s worth checking but unlikely to be an issue I would think.

Do you actually have side air bags? You would get this fault if someone replaced the module from another vehicle (with air bags) and didn’t re-code it for a car without. If your car has side air bags you will have a 2-part door card leather insert And a small plastic plug with SRS on it. Side air bags are rare on a Z3 and were a special build option in the factory. My gut feel is that’s your issue.

Do you definitely have a bulb in the dash for the air bag light? If above is correct I would probably have expected them to remove bulb to pass MOT.

 

[ZedEyez]

Yes definitely got side airbags. I have original bill of sale and it’s listed as a paid for upgrade. Also have small airbag plastic plugs in door cards.

I haven’t physically checked for a bulb in the dash but it is lighting up but mostly dim. I’ll post a picture

 

[ZedEyez]

 

[mrscalex]

[QUOTE="ZedEyez, post: 689497, member:
I haven’t physically checked for a bulb in the dash but it is lighting up but mostly dim. I’ll post a picture
[/QUOTE]

I think the big clue here is errors on both. So I think you look towards upstream commonality or downstream fiddling. My next port of call would be pulling the door cards off to have a poke. But a replacement module that hasn’t been recoded may still be your problem. Now the theory is a replacement module has gone in from a car without side air bags but the module has discovered something connected. I have had exactly this issue before and that’s what it was.

 

[colb]

The light may well be dim if the bulb has been removed there is a secondary small led that will glow if fault remains and main bulb is removed, like Rob I am suspicious of both sides showing up as errors would at least check connections behind door cards then look upstream from them to the module

 

[mrscalex]

The light may well be dim if the bulb has been removed there is a secondary small led that will glow if fault remains.

Wasn’t aware of the secondary led. But did think light might be leaking in from the hole if bulb removed making it look illuminated.