C8 - airbag fault but not the airbag...

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C8 - airbag fault but not the airbag...

Post by lifechooser » 12 May 2018, 17:10

I have an intermittent airbag fault which flashes up from time to time, usually when the car is heavily loaded and cornering... Lexia 3 pointed to the side curtain airbag, so I set about replacing it with the one from my scrapper. I removed the one from the scrapper first so I could learn how to do it without worrying about damage, but I knew I was onto a loser when I started dismantling the working car and discovered that the airbag in place had "807" scrawled on it in scrapyard pen. Someone had clearly tried to fix this before I tried.

Anyway, long story short, I've replaced the airbag which was showing the fault, to no avail. What could the issue be? The old car is off to the scrapyard this week, so if I need to get something out of it, I've only got a few days.
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Re: C8 - airbag fault but not the airbag...

Post by Gibbo2286 » 12 May 2018, 17:26

I don't know the C8 well but on the C5 there are three most likely causes, the connections under the seats, a connection behind the bulkhead trim where the passenger's feet reside and the Comm 2000 unit under the steering wheel, I've fixed two of those and they were both faults in the Comm 2000.
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Re: C8 - airbag fault but not the airbag...

Post by GiveMeABreak » 12 May 2018, 18:25

It would be helpful if you had the Lexia Code for the fault as there are hundreds of fault codes - As Gibbo says the Airbag ECU may have a trapped or bad connection. It is located on the floor between the 2 front seats as in the following:
C8 Airbag ECU.PNG
If you can get me the codes, I might be able to locate some further info for you.
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Re: C8 - airbag fault but not the airbag...

Post by Paul-R » 12 May 2018, 18:40

Does the C8 have an ECU for the airbags like the Mk1 C5 that I used t have? When I replaced the seat airbag that had blown I also had to replace the ECU as this had stored error and kept saying the airbag was still blown.

On the C5 the ECU was located under the centre console forward of the gearlever. I had a spare ECU from a donor C5 but I believe that there are firms that can virginise the ECU.
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Re: C8 - airbag fault but not the airbag...

Post by Paul-R » 12 May 2018, 18:42

Marc has clarified where the ECU is located but it may still need replacing.
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Re: C8 - airbag fault but not the airbag...

Post by GiveMeABreak » 12 May 2018, 18:45

Hopefully as the OP has a Lexia we can get some codes to help ascertain the fault. I'll see what we can see about the ECU itself in the meantime.
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Re: C8 - airbag fault but not the airbag...

Post by GiveMeABreak » 12 May 2018, 18:48

Ok, so confirmed that int he event of an actual airbag activation - both the airbag and ECU must be replaced.
In the event of only a minor impact, where only the seat belt pretentioners are deployed, then the ECU can be retained.
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Re: C8 - airbag fault but not the airbag...

Post by lifechooser » 12 May 2018, 19:41

I had two fault codes showing on Lexia;
Fault (E691) : RH side and RH side curtain airbag igniters in series Open circuit
Fault (A9B9) : Fault not listed
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Re: C8 - airbag fault but not the airbag...

Post by lifechooser » 12 May 2018, 19:46

I've removed the SRS ECU from the scrapper (thanks for the location). The good news is it only took 10 minutes. The bad(ish) news is that in doing so I ripped the carpet - it's a layer of foam sound deadening, board and then carpet - trying to lift the section over the airbag module snapped the board and ripped the entire 1ft section between the seats out. Looks like when I swap it on the real car I might need to remove one of the seats. I tried doing this on the scrapper a few weeks ago and failed, there are so many bolts I'm not sure which are the right ones to use. I'll google it. At least I know not to make the same mistake on the main car.
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Re: C8 - airbag fault but not the airbag...

Post by lifechooser » 12 May 2018, 19:48

Off topic - is there anything else I should remove and keep from the scrapper, just in case?
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Re: C8 - airbag fault but not the airbag...

Post by GiveMeABreak » 12 May 2018, 20:11

This is is the only one I have and the vehicle is a bit too old for me to get any further extended data on the troubleshooting of the fault.
E691: Right-hand side airbag and right-hand side curtain airbag in series ignition modules fault: Resistance too high

So try and check out those wires to the ECU and see if one is chaffed somewhere (usual safety precautions working on Airbag systems of course :) )
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Re: C8 - airbag fault but not the airbag...

Post by wheeler » 12 May 2018, 22:23

On the C8 that fault code is normally caused by a faulty splice under the carpet near the sill, if I remember right you need to take the seat out to get to it, you cut the old one out & resolder & heatshrink.
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Re: C8 - airbag fault but not the airbag...

Post by aneesh84 » 12 May 2018, 22:48

Seems like too much trouble. Why not just disable the airbag.
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Re: C8 - airbag fault but not the airbag...

Post by GiveMeABreak » 12 May 2018, 23:12

Because our UK MOT laws are obviously stricter than yours!

UK MOT rules state a factory fitted airbag obviously missing or not operational is a MAJOR failure. But more than that, insurance companies may decline to pay out for an injury sustained as a result of disabling safety systems and this Forum does not support this action.
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Re: C8 - airbag fault but not the airbag...

Post by Hell Razor5543 » 12 May 2018, 23:26

It is also possible that, with the new MoT regulations coming in, a faulty airbag system could be classified as 'Dangerous', and that means the vehicle cannot be driven away from the test centre!
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