knee Airbag igniter fault - short to ground

[aw911]

Hi

Hoping for some assistance with regards to a fault that has started reporting on my Audi A6 3.0tdi.

The fault is front passengers knee airbag igniter - short to ground.

Tried resetting it with Vagcom but fault comes back immediately. Therefore I stripped out the passenger side glovebox to check the connectors. What I have found is that there is actually no knee airbag on this side of the car....there are also no connections present for a knee airbag on this side. The airbags in the upper dash are present and I removed and refitted the connections for these just to see if that would affect the fault.

Advanced measuring values showed that there was a 'too high' value reporting on the drivers side knee airbag igniter so I wondered if this was causing the issue. Therefore I stripped out the drivers side lower dash....only to find that there is no knee airbag on this side either? Again there are no connectors present for airbags either.

This has obviously left me a bit confused. I have owned the car for nearly a year now with no issues and the fault only started reporting last month for no apparent reason. The fact that there are no airbags fitted in these locations is what is confusing me?

Any advice would be gratefully appreciated. I would post pics up but I am unable it seems to attach photos to the thread.

[VAG-Abound]

Our seats started giving a too high error at some random time. It's quite common with various of the airbag layouts, due to resistance getting too high for some reason in the multiple controller to airbag connectors. As fitted there are two in our seat: one at base of door pillar, one under the seat. Cutting out the pillar one and crimping wires fixed it for me.

Not having the bags makes it difficult to do this of course :). What are the actual error codes?

Can you see the resistance in the other circuits in VCDS? I was able to use a pencil lead and croc clips to figure out what resistance would keep the system happy, and popped resistors in from Maplin as a stop gap until I got the bit of loom that I needed.

[aw911]

Hi

Thanks for the reply.

The fault code in Vagcom is 9440785

Front passengers knee airbag igniter B100E 11 (137) - Short to ground

I've just removed the entire centre console and disconnected and reconnected the airbag module in case that is the issue...no change to fault.

I wonder if anyone has the wiring diagrams for the A6 C7 2012 3.0tdi S-line Quattro. Given that there are not actually any knee airbags in this vehicle I'm figuring that I could perhaps cut the wiring just after the plug assembly and the solder some resistors in line which would then clear the fault code.

Really frustrating as there is no reason why it has come on....all I can surmise is that perhaps a wire has been chafing somewhere or been caught and has finally created this issue even though the actual airbags don't exist in this vehicle.

No point taking it to Audi as they will just want to take my pants down to investigate a fault like this!

I would post pictures up but there seems to be no way to do this via a mobile phone browser?

[aw911]

Well I've stripped out the centre console and the left hand side b pillar and left hand side lower trim so I can get to the plugs for the airbags on that side. Located plug 17p in that area and checked the wiring....none of it shows continuity to earth on either side of the plug.

Then went to the airbag ecu plug. The wiring diagram I have shows pins 45 and 46 as being the pins to the passenger side knee airbag..... well I don't even have those pins present so now I'm questioning whether I even have the right wiring diagrams for the A6 even though it shows Audi A6 all over it.

Frustrated as hell right now. The only pins that bell out to earth at 75 ohms are pins 51 and 76 which are both black and white stripes.....

Wondering if the actual airbag control unit is faulty....given that the wiring does not bell out to earth which implies that there is no short to earth?

Any advice appreciated....or even some wiring diagrams for the airbag circuits.....just in case mine are actually incorrect. My diagram shows that pins 45 and 46 on J234 go to the pass side knee airbag and that pins 43 and 44 go to the drivers side knee airbag....i don't have these items fitted and the pins aren't present in the main airbag control unit plug J234.

Thanks in advance

[VAG-Abound]

What airbag modules show in VCDS? Have the knee ones been coded in by mistake?

[aw911]

Just rebuilding the car so i can drive it at the moment. Will reconnect once I'm done and get some screenshots of the coding data for the airbag module.

I've owned the car for 12 months now and the fault only arose a few months ago.....the module has not been coded or had the code changed in that time?

I understand what you are saying....maybe if someone without knee airbags fitted could send me a shot of the long coding from their VCDS then I could perhaps try recoding my module? Or at least compare the coding.

Contacted Audi for a price on a new airbag control unit.....£680 plus VAT !!

The investigation continues....however I'm getting good at removing audi interior panels which will stand me in good stead when I install the reversing camera at a later date.

[aw911]

So I've refitted everything I removed....Needless to say the fault is still present. Given that the wiring for those components does not even exist in the plug or the car I can only surmise that the Airbag control unit may be faulty.

I've checked the status of the components and knee airbags are not toggled in the control unit whereas the other airbags etc....show as 'activated

Therefore I've ordered a 2nd hand airbag control unit to slave in and see whether that changes or clears the fault....ive also taken a note of the long coding in case I need to recode the module that arrives.

[aw911]

So I've received a replacement airbag module from Lithuania.....same part number etc....
Have swapped it in but now have come up against the 'component protection ' issue.
Cleared all faults on replacement airbag module with Vagcom....but unable to clear the component protection fault.....which keeps the airbag light on.
Long coding can also not be altered using Vagcom....but this may be due to the component protection issue.
There are lots of threads on ODIS etc.....being used to remove component protection in conjunction with VAS 5054A Interface....however I can't see how you can actually do this unless you have a license and access to the online server to enable you to remove componet protection.
Does anyone know of any independents in East Sussex that offer this service....or am I going to have to go into a main Audi dealer?
Has anyone successfully removed component protection using ODIS software and the VAS5054A interface purchased off one of the many sellers online?

[jaketson]

Did you find a solution?

[aw911]

Yes and no.....when the car was in my garage and fixing the coolant leak in the centre of the engine for approximately a week I found that the fault cleared ok using VCDS and didn't come back for a few months. It has since come back again and won't clear using VCDS

As I said in the thread the wiring is not present.....there is no knee airbag as it is not specified on this particular model. My thinking is that the problem is moisture related and that this is creating an issue which is causing this reporting fault.

I'm going to get to the bottom of it at some point. Need to address the issue with the front passenger door where you sometimes get water ingress during heavy rain that has been mentioned in the forum previously so perhaps that will have an effect. Electrical faults of this nature are always difficult to diagnose unfortunately 😕

[Totila]

I'm having the same problem. Did you get to the bottom of it by any chance? A local garage also suggested i replace the airbag module and they'll remove the CP and code it, but i'm afraid the code will still be there.

[philipharmes]

I wouldn't be surprised if it wasn't water ingress into the wiring or a connector.

Get the floor carpet loosened both sides ( passenger & driver ) & get your hand in under the foam which is under the carpet.

Check to see if any wetness under there.

[Totila]

Its no water. My car is garaged :(

[Abick]

Hello
I have the same problem. Are you by any chance the cause of this problem? I would really appreciate any help
thanks.

[S shah]

Guys did you found resolution to the problem, i got the same issue?

[VAG-Abound]

Guys did you found resolution to the problem, i got the same issue?

What fault code are you seeing, with what reader?

[S shah]

B100911
Driver side, rear seat belt tension igniter Short-circui

[VAG-Abound]

B100911
Driver side, rear seat belt tension igniter Short-circui




On what car?

There may be some yellow plugs at the bottom of the pillar behind the door. With battery disconnected (to avoid embarrassing deployment of airbags) unplug them, then battery back on and scan to see if fault changes to "open circuit / resistance high". If so it'll be a problem in the wires from plug to igniter.

[S shah]

On what car?

There may be some yellow plugs at the bottom of the pillar behind the door. With battery disconnected (to avoid embarrassing deployment of airbags) unplug them, then battery back on and scan to see if fault changes to "open circuit / resistance high". If so it'll be a problem in the wires from plug to igniter.



The problem is there is no wiring to the seat belt as its for american market only. so the car is giving alarm for system which is not there in the car.

[VAG-Abound]

Several threads on phantom shorts to non-existent airbag circuits have been inconclusive, but I think where it is fixed people usually decide that is water or age damage to the airbag controller.

[Ithinker]

This happened to me and I was trying to figure out why

The way I fixed it was unscrewing the right bolt right under the glovebox and then cleared the codes
(Not the bolt inside the glovebox. it’s the one closest to the passenger door under the glovebox, you can access it without opening anything)

As soon as I screw the bolt back in the fault comes back

I love German engineering!!

[TTTateca]

Any advice would be gratefully appreciated.

Pin 43 and pin 44 are filtered to GND by a block capacitor, on the PCB, next to the input pins. One of the capacitors has failed and become a resistor to GND, thus the error reported. Solution is to remove the capacitor block from the circuit, as it is not needed anyway for EU markets. If you want to confirm the fault, just measure the GND plane against pin 43 and pin 44, one of it will have a resistance of less than 1.8 kohms.