55 Plate 1.6 Picasso Desire airbag issue

[Hell Razor5543]

There are several airbag ECUs in a car. I recall I had a problem with my last car, in that the passenger airbag light was permanently lit. After a Lexia session it was found that the left airbag ECU was not communicating with the main airbag ECU. I replaced that suspect ECU (it could have been the wiring between the two), and that resolved the fault.

[Tam]

Thanks HR, interesting indeed. A novice to all this so trying what I can and searching the forum for tips etc. The garage's Lexia could not communicate with the ECU so it's a process of elimination I think. Just don't want to throw too much cash at it.

[Hell Razor5543]

On my Xantia there were three (possibly four or more) airbag ECUs. The primary ECU was under the trinkets tray in front of the gear lever (so it was likely to have enough time to work out which airbags to fire; if the impact was severe enough to destroy this ECU before it deployed the airbags the occupants would have been killed regardless of airbags), and one in each of the main door pillars (for detection of side impacts), near to the safety belt reels. I would expect one or more up at the front of the car as well, to help detect a frontal impact.

As I understand it, if there is an impact severe enough to trigger an airbag deployment the main airbag ECU locks up afterwards (so as to hold the information for any investigation). DHallworth (a forum member) bought a C6 that had been kerbed hard enough to trigger the airbags. He did manage to get the C6 completely sorted out, including getting the airbag ECU reset (but he may have replaced it). IIRC it could be communicated with after the incident.

[Tam]

It could be that the car had a bump as I've not long had it. Just a pity there are no comms with the ECU. I will keep plugging until the rest of my hair goes

[Hell Razor5543]

Here is the link to DHallworths' blog, hopefully starting at the relevant page;

http://www.frenchcarforum.co.uk/forum/v ... start=1005

I don't know if this helps, but it might.

[Tam]

Read a few pages mate, will get round to reading the rest...looks a cracking read.

[Tam]

After doing some more reading(Citroen Training manuals) It looks like(Hopefully) I can rule out BSI as that doesn't appear to have any bearing on the airbag ECU circuits. It said that airbag warning light on was not a fault with BSI......we shall see

[Tam]

Ok, I got the ECU I ordered delivered today, put it in, did the reset and lo and behold......the passenger airbag deactivated light came on as well as the drivers one Then I checked, the ECU was not the one I ordered so has been packaged up to be returned. It also looked a bit battered which it shouldn't. Another on order to arrive Tuesday...mmmmmm Ready to put this motor to bed tbh

[Tam]

Hi again guys!
I have now ruled the ECU out and have another question if I may?
The airbag was removed and when you turn it upside down to inspect it, on one side the there is a hole with a blue socket, that a plug fits in but, at the opposite side there is a plug that was pushed into the same type of hole but there is no socket in that hole. Plug sits kind of loosely in that hole, is this normal?
It just doesn't seem right but what do I know I have searched online for side views of airbag but no luck.

Again, any ideas or replies would be appreciated.

[GiveMeABreak]

Tam - a few pics might help us see the problem - 'sockets and holes' - a bit confusing to understand what you're trying to describe

[Tam]

Cheers Marc, just got them now trying to work out how to attach them

[Tam]

[Tam]

Whoever edited this...thank you! I looked in edit and now know how it's done......Cheers

As you can see, the left(Blue) has a blue socket to put the plug in but the right(Green) does not. It simply sat in that hole

[GiveMeABreak]

Well one is definitely the airbag plug. There are several plugs - horn, airbag, audio controls etc - all depends on kit. I can't tell you which is which though Tam. The driver and passenger front airbags generally have a 2 stage igniter depending on the severity of the impact. detected by the sensors, which informs the airbag ECU, which determines whether the igniters should both discharge together resulting in a quicker more forceful impact or whether a single igniter fires in a less severe impact, with the second igniter following shortly afterwards (to ensure it does not get triggered later if emergency services are in attendance for example). I'll have to do some digging!

[Tam]

As ever Marc, much appreciated, just find it strange that the green plug doesn't have a socket to plug into! As I said it was just sitting in that hole where I imagine a socket should be. Without seeing side views of other airbags..i'm stumped.......not hard I know