air bag ecu

This is the Forum for all your Citroen Technical Questions, Problems or Advice.

Moderator: RichardW

Post Reply
2cvandy
Posts: 66
Joined: 01 Jul 2013, 00:17
Location: Mayenne, France
My Cars: 2002 C5 break, 2.0HDI
1989 2CV
x 12

air bag ecu

Post by 2cvandy »

Not sure where to start with this question as I'm pretty sure I have more than one problem, but here goes,

firstly, can anyone tell me if my car should have an air bag warning light? It's a 2002 C5 110 HDi Exclusive estate.
I know that might sound like a stupid question, but these air bag things are all new technology to me, my other car is a 2CV!

The reason I ask is that my car displays "airbag fault" every time I start it up, I've had it on a Lexia and that says "airbag ecu fault (VAN internal)".
Now I took that to mean that the airbag ecu was faulty, and as I didn't want the car off the road while I sent it off to be repaired, I bought a 2nd hand ecu (same model, same code no's) and fitted that. Of course the fault persists because nothing is ever that simple is it?

However, it's only while reading up on this that I realised that there is no air bag light on my dash when I first turn on the ignition. So now there are more questions ;
Should there be a light? or is it not fitted on this model because it has the central warning display?
If it should have a light, is it possible / likely that the none illumination is also being caused by a faulty air bag ecu? or is it more likely a previous owner took the bulb out?

Finally, if anyone knows exactly what "airbag ecu fault (VAN internal)" means and can point me to a fix I'd be grateful,,,,,,,,,,,,,,,
If speed kills, buy a 2CV and live forever.
Online
Gibbo2286
(Donor 2020)
Posts: 7171
Joined: 08 Jun 2011, 18:04
Location: GL15***
My Cars: 2006 C5 2.0 Litre HDI VTR Automatic Estate.(now sold on)
Currently Renault Zoe 2014 ZE
x 2500

Re: air bag ecu

Post by Gibbo2286 »

Air bag lights, some do some don't, it depends on the car spec. I'd guess yours doesn't.

The usual problems with 'air bag fault'' warnings are poor wiring connections under the front seats or under the carpet covering the bulkhead by the passenger's feet (RHD cars) but the most likely cause in my experience is failure of the Comm 2000 unit internal wiring.

The Comm 2000 is the bit with all the wiper and lighting stalks below the steering wheel, it can be replaced without much difficulty by a competent do it yourselfer, used ones are about but you must be sure to get the right one as there are quite a few variations.
Man is, by nature, a lazy beast, he does not need twice encouraging to do nothing.
2cvandy
Posts: 66
Joined: 01 Jul 2013, 00:17
Location: Mayenne, France
My Cars: 2002 C5 break, 2.0HDI
1989 2CV
x 12

Re: air bag ecu

Post by 2cvandy »

Hiya,
thanks for the reply,
the connections under the front carpets were replaced following advice on here when I first bought the car (prior to getting the Lexia on it, no change.
The Comm unit has just been overhauled by Grahame in Bradford as it had a couple of other faults, he tested it for the airbag fault and says that's not the cause.
It appears that it's down to the ecu, just not sure if it's the ecu itself or the wiring to / from it?
Hence my asking about the airbag light, but if some models didn't have one I guess that's not down to the ecu at least!

Anybody else got owt to add?
many thanks,,,,,,,,,,,,,,,,,,,,
If speed kills, buy a 2CV and live forever.
User avatar
myglaren
Forum Admin Team
Posts: 25366
Joined: 02 Mar 2008, 13:30
Location: Washington
My Cars: Mazda 6
Ooops.
Previously:
2009 Honda Civic :(
C5, C5, Xantia, BX, GS, Visa.
R4, R11TXE, R14, R30TX
x 4889

Re: air bag ecu

Post by myglaren »

I'm reasonably sure that there should be an airbag light and it should light up on turning the ignition on, along with the others, then go out a few seconds after engine start - along with the others.

I did have mine come on on a couple of occasions when the charge on the battery was a bit low, went out after recharging the battery.
That was on a 2002 SX. Never seen it on the current one.
I'll have a look on mine when I go out later on.
2cvandy
Posts: 66
Joined: 01 Jul 2013, 00:17
Location: Mayenne, France
My Cars: 2002 C5 break, 2.0HDI
1989 2CV
x 12

Re: air bag ecu

Post by 2cvandy »

myglaren wrote:I'm reasonably sure that there should be an airbag light and it should light up on turning the ignition on, along with the others, then go out a few seconds after engine start - along with the others.

I did have mine come on on a couple of occasions when the charge on the battery was a bit low, went out after recharging the battery.
That was on a 2002 SX. Never seen it on the current one.
I'll have a look on mine when I go out later on.
Cheers,
what model is yours?
If speed kills, buy a 2CV and live forever.
dnsey
Posts: 1538
Joined: 20 Oct 2004, 01:39
Location:
My Cars:
x 19

Re: air bag ecu

Post by dnsey »

Is the ECU clever enough to detect a blown/removed warning lamp, and to display the fault warnng as a result?
2cvandy
Posts: 66
Joined: 01 Jul 2013, 00:17
Location: Mayenne, France
My Cars: 2002 C5 break, 2.0HDI
1989 2CV
x 12

Re: air bag ecu

Post by 2cvandy »

dnsey wrote:Is the ECU clever enough to detect a blown/removed warning lamp, and to display the fault warnng as a result?
Good question,,,,,,,,,,,,,,,, anybody know?
If speed kills, buy a 2CV and live forever.
wheeler
Posts: 6848
Joined: 21 Sep 2002, 19:07
Location: United Kingdom
My Cars:
x 717

Re: air bag ecu

Post by wheeler »

I believe only the base model mk1 C5's have an airbag light, my SX definitely doesn't.
Its a strange fault code, normally the footwell connectors & the com2000 faults log a different fault code relating to the igniter circuit. I don't think I've seen a mk1 C5 yet with any under seat connection problems, they dont suffer the same as older models as the pretensioners are in the inertia reels in the B pillar rather than the stalks on the seat.
Next thing i would do here is obtain the wiring diagram & check the continuity of the 2 data wires on the body VAN network & also check they are not shorted to earth.
Don't ever probe an ohmeter into airbag system wiring though unless you are 100% sure that the wire is not on the igniter circuit, ohmeters send out a small current to make measurements which carries a risk of deploying the airbags.
User avatar
myglaren
Forum Admin Team
Posts: 25366
Joined: 02 Mar 2008, 13:30
Location: Washington
My Cars: Mazda 6
Ooops.
Previously:
2009 Honda Civic :(
C5, C5, Xantia, BX, GS, Visa.
R4, R11TXE, R14, R30TX
x 4889

Re: air bag ecu

Post by myglaren »

2cvandy wrote:
myglaren wrote:I'm reasonably sure that there should be an airbag light and it should light up on turning the ignition on, along with the others, then go out a few seconds after engine start - along with the others.

I did have mine come on on a couple of occasions when the charge on the battery was a bit low, went out after recharging the battery.
That was on a 2002 SX. Never seen it on the current one.
I'll have a look on mine when I go out later on.
Cheers,
what model is yours?
2.0 HDi 110 SX 2003.
Just checked and it doesn't light on ignition with the rest of them.

Thinking back, it was the centre display that threw up an "Airbag Fault" display.

I was under the impression that for MOT purposes the indicator had to light on first position of the ignition key and extinguish after about ten seconds or it was MOT fail. Mine has never been mentioned at MOT time so I must be wrong on both counts.

Information in the handbook is sketchy to say the least.
User avatar
Stickyfinger
(Donor 2016)
Posts: 10411
Joined: 28 Mar 2013, 21:05
Location: Somset my lovleee
My Cars: Xantia V6 ACTIVA 3ltr 24v Manual p1
Xm 2.1TD Ph2 Exclusive
AX, little Daffodil
SAXO White Mk1. Sally
x 1280
Contact:

Re: air bag ecu

Post by Stickyfinger »

The other option is rubbed wires withing the plastic protector that hangs below the seat....yep, mine had sharp edges on the plastic inside the molding that caused a light as it rubbed thru the two wires (reported as AirBag ECU on Lexia), just needed some insulation to fix it, only found it as I was switching seats and also swapping the AirBags over as well otherwise I would never of thought to look.
Alasdair
Activa, the Moose Rider
3x C5x7 Steering racks and counting
2cvandy
Posts: 66
Joined: 01 Jul 2013, 00:17
Location: Mayenne, France
My Cars: 2002 C5 break, 2.0HDI
1989 2CV
x 12

Re: air bag ecu

Post by 2cvandy »

Thanks for the replies guys, I'm on holiday at the in-laws at the moment but I'll check out the ecu wiring for any dodgy connections next week when I'm back home.
Looks like I might be needing a good sparks to do a system check on it though.
MOT not due until July so hopefully we'll crack it before then!
Got to say though, other than the fact that I kinda resent having a car that's cleverer than me, it is a damned good motor. Just glad I've got the 2CV to use when this one has a headache.
If speed kills, buy a 2CV and live forever.
Post Reply