Mistifiying airbag light

[Jezza]

Hi there, I hope somebody can help me with something odd. I bought a 2000 Z3 2.2 a month ago from a guy in Cornwall. The car seemed to be well looked after, but on the drive home to Yorkshire the airbag light started to flicker, but it was very faint. It only happened occasionally. Upon investigation at home I found that when the ignition is turned on, the airbag light doesn't actually light up. I didn't notice this when I bought the car - I only checked for no dashboard fault lights being on once the car was running, which is what you expect. I took out the instrument cluster a few days ago, only to find that the airbag bulb had actually been removed. I also bought an airbag light reset tool and checked the system for faults. The tool fails to communicate with the airbag module.
Now I understand why the airbag light doesn't come on and go off when the ignition is turned on, but I am absolutely mistified as to why the airbag light comes on during driving when there isn't even a bulb there!! There are no other warning light coming on that could possibly 'bleed' light through into the socket for the airbag bulb, and I just can't understand where this light is coming from. Any ideas out there?

 

[Shelly]

 

[Duncodin]

When the airbag bulb is missing there is a faint glow from other lights in the dash shining through the hole/socket where the bulb was.

Get a new bulb and put it in the hole. Maybe that new bulb will then light up properly telling you to go looking for the actual problem.

 

[t-tony]

Should've failed the MOT test with that fault as it cannot be working correctly. If the airbag light does not illuminate when you turn on the ignition and extinguish a few seconds later then there is a fault and the SRS system will not work in the event of a crash. If the airbag light does not illuminate when you turn on the ignition that is a fail straight away.

Tony.

 

[Mint]

Hi Jezza and from me too in Stafford. I'm sure I read somewhere [can't remeber where] that there is a small board mounted LED which sits underneath the normal lamp. So if the lamp is removed the small tell tale light will be from the LED.

 

[Jezza]

Hi Mint. If that is true then it would explain the symptoms I am seeing. Today I took the cluster out again and put a new bulb in. I expected the airbag light to be on all the time if there's a problem. But no, upon starting the ignition, no lights are on. As yet no light is showing but I haven't been for a drive, only run the engine.

 

[Mint]

As Tony said above, the airbag light should come on with the ignition then go off after a few seconds when the system has gone through its checks. If it doesn’t light up at all you definitely have a problem.

 

[BoxClever]

I think I have the same missing bulb problem, there is a bit of spill faintly illuminating the airbag symbol. Annoying as the car came with a full MOT and it couldn’t have truthfully passed. So it’s on the list of niggles to sort!!

 

[Duncodin]

I think I have the same missing bulb problem, there is a bit of spill faintly illuminating the airbag symbol. Annoying as the car came with a full MOT and it couldn’t have truthfully passed. So it’s on the list of niggles to sort!!

It is quite faint. Maybe not immediately noticeable in broad daylight or well lit inspection bay.

 

[Mint]

...I'm sure I read somewhere [can't remeber where] that there is a small board mounted LED which sits underneath the normal lamp. So if the lamp is removed the small tell tale light will be from the LED...

Found it, post #7 in this thread...https://www.pistonheads.com/gassing/topic.asp?h=0&f=72&t=743931

 

[colb]

I believe there is a secondary led in there, thats what you are seeing glowing when there is no main bulb in there. To check the system you need to look in INPA to see if its doing its readiness checks and code read it to see what codes have been set. Nightmare these airbag systems, currently trying to sort a members Z4 with airbag light showing and not clearing. Using INPA and BMW Scanner 1.4 and a Crreator 310+ to scan it. Garage had told him it was the passenger satellite module gone bad, we tried replacing that with same number used module which made no difference. Scanned it again and I came to the conclusion the fault was in the main module behind the handbrake showing a code of 93DB - step up converter defective. A used same number module was obtained and this was fitted scanned the original fault code was gone but we were presented with another showing Incorrect Vin Number was in trhe module. Attemps to change the Vin using NCS Expert and Winkpf as others have successfully done didn't work for us. Got to explore further using Tool32 which apparently can be used to change the Vin in the replacement module. The airbag light remains on until we can change the Vin Number and clear the code, I am preety sure thats all thats needed to get the light off.

 

[BoxClever]

It is quite faint. Maybe not immediately noticeable in broad daylight or well lit inspection bay.

Yep, I didn't notice it for over a week of ownership and took some convincing after the amazement that one of the previous owners will have actively done this, and the car has a very recent MOT. Annoying but fixable.

 

[Jezza]

Well the mystery is explained- thank you Mint. I took the cluster apart this morning and I can clearly see the location of the board mounted LED, and it has a little side tunnel into the airbag light chamber. It makes sense that there would be some kind of backup light for the airbags in case of incandescent bulb failure. So obviously I do have an airbag problem to solve but at least my brain can now concentrate on that rather than a ghost light!! Ordered a Creator 310+ scanner so hopefully this might give me a clue.
Thanks to everyone who's chipped in. Much appreciated!

 

[Mint]

Well done, at least you proved my theory. Now you can fix it properly

 

[Jezza]

Hope so!

 

[Morfhieus]

Hi there, I hope somebody can help me with something odd. I bought a 2000 Z3 2.2 a month ago from a guy in Cornwall. The car seemed to be well looked after, but on the drive home to Yorkshire the airbag light started to flicker, but it was very faint. It only happened occasionally. Upon investigation at home I found that when the ignition is turned on, the airbag light doesn't actually light up. I didn't notice this when I bought the car - I only checked for no dashboard fault lights being on once the car was running, which is what you expect. I took out the instrument cluster a few days ago, only to find that the airbag bulb had actually been removed. I also bought an airbag light reset tool and checked the system for faults. The tool fails to communicate with the airbag module.
Now I understand why the airbag light doesn't come on and go off when the ignition is turned on, but I am absolutely mistified as to why the airbag light comes on during driving when there isn't even a bulb there!! There are no other warning light coming on that could possibly 'bleed' light through into the socket for the airbag bulb, and I just can't understand where this light is coming from. Any ideas out there?

I actually just had the same issue. I bought a Non running car just last week and noticed that my airbag light would not illuminate, but I wiggled the key and fiddled with the ignition and was not only able to get the airbag to light to light, but get the car to crank. I traced it to a bad Ignition switch.

BMW cluster does not require a signal to light the airbag light, but DOES require one from the SRS module to extinguish it. My issue was no power to that portion of the cluster to begin with... Hope that helps you. Mine is perfect now after replacing the switch.

 

[Jezza]

Further to my last post I got the Creator 310+ scanner. Plugged it in (under the bonnet) but alas the airbag module cannot communicate with the scanner so I am none the wiser. Can read other stuff but not the SRS module. I guess the airbag control module is goosed then? Is that located on the transmission tunnel behind the radio/heater facia? Looks like a pig to get at...

 

[Morfhieus]

Further to my last post I got the Creator 310+ scanner. Plugged it in (under the bonnet) but alas the airbag module cannot communicate with the scanner so I am none the wiser. Can read other stuff but not the SRS module. I guess the airbag control module is goosed then? Is that located on the transmission tunnel behind the radio/heater facia? Looks like a pig to get at...

It is located in the center of the car under the console. I would first verify power and earth before condemning the srs module. In the dealership, we were trained NOT to use any sort of jumpers at the srs connector. The one at the srs module itself doesn't have the safeties against blowing any of the bags.

 

[Tearoom]

Yep, I didn't notice it for over a week of ownership and took some convincing after the amazement that one of the previous owners will have actively done this, and the car has a very recent MOT. Annoying but fixable.

Hi, where abouts in Bristol are you?
I have an airbag reset scanner. I replaced my interior last year (as i was bored in lockdown) and didn't notice that the seat belt tensioners had been fired on the 'new' seats. Naturally when i put everything back together my airbag light stayed on. I replaced the tensioners and had to reset the airbag sensor so the light would go off.
A lot of people replace their seat bushings and get issues with the airbag light staying on, so if you ever need your airbag sensor resetting, i'm not that far away.

 

[BoxClever]

Hi, where abouts in Bristol are you?
I have an airbag reset scanner. I replaced my ….

Thanks mate, I’m near Cribbs - BS34 - and would be great if you can have a look. Or maybe I can come to you?