C5 mk1 pretensioners

[evilclive]

The MOT man took exception to the state of the pipes in our Xantia, so we needed a new car in a hurry and I'm now the proud(ish) owner of a 53 plate C5 HDi.

While driving along, a pothole leaped out without looking and we hit it with a bang. On restarting the car a couple of miles later, it's now complaining that the pretensioners have fired. Which I don't think is true (the bang was outside and sounded like hitting a pothole, not inside, the belts run fine, no evidence of anything going bang inside).

I've read elsewhere the fix for this is new (ie s/h) airbag ECU, which is cheap enough to try. Has anybody here tried this, and is there anything I need to know? I've got a lexia. Also anybody know how to tell if a pretensioner really has fired?

(at some point I'll work my way up to thinking more about the lack of power, the LH window/mirror not working and BSI saying no computer there, and the rather more scary possibility of repiping the Xantia, but for now I'd like to not have something simpleish to fix )

[GiveMeABreak]

I wouldn't even think about parts until you have found the cause. If it was a savage pot hole it may well have upset something like a wire or a connection - but you absolutely need to get it talking to your lexia to determine where the fault is.

As for your Lexia saying there is no BSI - you may have an older VCI that won't talk to a CAN vehicle - this is a known issue with the C5 and Peugeot 308 as examples. Get that working first and then you can focus on the Pretensioner issue.

[evilclive]

I have plugged it into the lexia - it says the pretensioners have fired. Both of them, so not a loose connection. Either they've both fired, or something else has happened.

It's not that there's no BSI, it's the BSI saying there's no computer (or is it module) for the door where the window and mirror don't work. Which I'm guessing is a loose wire somewhere, and when I'm feeling keener I'll look.

[GiveMeABreak]

Ok that’s clearer. That’ll likely be the driver’s door control module. That controls the windows and mirrors and a few other components. Check the umbilical wiring tube from the a pillar to the door. It is possible a wire has broken in there.

[evilclive]

Yes, a wire there was going to be my first guess. But it's not annoying me too much (it's LH, ie passenger side), whereas the pretensioner thing is MOT fail (not that it's for a while) and I think I'd prefer them to be working if possible.

[wurlycorner]

I had this problem following a minor accident in my C5 - check my profile (link in sig below) and you should find all the pics and info on what to check/what happened.

My pre-tensioners genuinely had fired, so I changed the seatbelts with ones from a scrap yard, then found I had to change the ECU as well (It would not reset from Lexia).

[GiveMeABreak]

It isn't uncommon for potholes to cause seatbelt pre-tensioners and even airbags to fire off. The Ford Fusion (in the states at any rate) has a damper that limits the travel of the struts when the sensors detect a pot hole, thus stopping the wheel from dropping into the hole - check the short video out - we definitely need this sort of tech with the state of the roads in this country getting worse:

Anti Pothole Technology!

[evilclive]

Thanks Iain, an interesting read - don't think I'm going to be as keen as you with mine

You mentioned smell of explosives, which implies it's pretty obvious when they've fired - was that the case? And no need for any recoding for a replacement airbag ECU?

(I've found various people who will clear the EEPROM - sounds a common enough problem).

[wurlycorner]

It was a pretty light smell tbh.
From memory, if you unbolt the tensioner unit and shake it, you hear a rattle if it's gone off. If no rattle, then they haven't fired.

I'm a bit confused why an aftermarket erase of the codes would work any better than clearing using the Citroen Lexia tool...
I have a thought that something 'blows' inside the airbag ECU when they are fired (a fuse or fusable link or something) which is why the code can be cleared, but re-appears immediately the ignition is put back on again.
My assumption is this would be either deliberately to ensure the safety system has to be properly repaired, or to protect the rest of the electronics in the car from any electrical spike/back EMF created when they fire???
That's not based on any 'fact' though, just my surmising...

[RichardW]

There might be an indicator on the reels to show they have fired. If you were to fit new reels you might find the light goes out, otherwise new ECU / repair of existing unit required.

[evilclive]

Re the airbag ECU and codes - it appears that the "I've fired things" is written to eeprom, and there's no programmatic way of getting it off, the software isn't designed to do it even with Lexia.
I think the aftermarket version is a dismantle and hack the eeprom - eg http://www.northernautotech.co.uk/airbag.html. So yes, it's something which "blows", but it's not quite as hard as a fuse, it's a software equivalent. And yes, I reckon it's to prevent people putting crash damaged cars back on the road without checking they're properly fixed.
I shall go and take the thing apart and have a rattle.
(yes, I know the precautions )

[GiveMeABreak]

The info regarding the state of the Airbag ECU I have states (translated from French) "After the airbags are triggered, the airbag computer goes into lock mode. The trigger information of a pyrotechnic element is saved. It is totally impossible to erase the defects."

The notes have the following in case it is of help (I've only extracted the part for the Pre-tensioners):

Triggering With Impact

Pyrotechnic devices activated	Compulsory replacements	Optional replacements
Pre-tensioning buckle (Simultaneous driver and passenger operation)	Pre-tensioning buckle strap (If seat belt worn : Inertia reels ; Return adjustment)	Pre-tensioning buckle strap (If seat belt worn : Stalk strap ; Return adjustment)
Pre-tensioning stalk (Simultaneous driver and passenger operation)	Pre-tensioning stalk - Return adjustment (If seat belt worn : Stalk strap )	If seat belt worn : Seat-belt stalk (If damaged) - If seat belt not worn, no changing of the buckle strap (Non pre-tensioning)
Strap return on stalk strap	Reel and belt return assembly(If seat belt worn : Return adjustment ; Seat-belt stalk )	If seat belt not worn, no changing of the buckle strap
Strap return on seat	Reel and belt return assembly(If seat belt worn : Return adjustment ; Seat-belt stalk )	If seat belt not worn, no changing of the buckle strap

Accidental triggering without impact

Pyrotechnic devices activated	Compulsory replacements	Optional replacements
Pre-tensioning buckle	Pre-tensioning buckle strap (If seat belt worn : Stalk strap ; Return adjustment)	If seat belt not worn, no changing of the stalk straps ; Return adjustment
Pre-tensioning stalk	Pre-tensioning stalk strap (If seat belt worn : Seat-belt stalk ; Return adjustment)	If seat belt not worn, no changing of the stalk straps ; Return adjustment
Strap return on stalk strap	Reel and belt return assembly(If seat belt worn : Return adjustment ; Seat-belt stalk )	If seat belt not worn, no changing of the buckle strap
Strap return on seat	Replacement of the triggered component (If seat belt worn : Return adjustment ; Seat-belt stalk )	If seat belt not worn, no changing of the buckle strap

[evilclive]

A grey weekend so I played with the car. I had a look at the tensioners (took the belt off, shook to check for rattles), and nothing untoward. Have ordered an ECU for not too much money, will see what it does.

Regarding the door - I took the door apart, and the reason for things not working was fairly obvious - not plugged in. I plugged it in, and then found out why it had been unplugged - it's got the C5 random window problem other people seem to have. (mirrors and temp sensor are fine).

Symptom - Open window, fine. Shut - goes to the top, then decides it doesn't like it there and comes back down a few inches. This happens nearly all the time. The first time it goes up there's a chance that it'll stay, so I've left it there for now. Passenger switch unplugged to stop people poking it unhelpfully
(while sending it up and down to see if I can manually get it to stop at the top, it also gets to a time where it gives up - motor getting hot, or ECU giving up? Wait a few minutes, engine on/off, and it starts winding again.)
I've tried a BSI reset - car seems to all work apart from this one window. Holding the switch at the top might work sometimes, but not reliably. Haven't plugged a lexia into it yet - maybe when I do the airbag ECU.

[GiveMeABreak]

With anti pinch you only need to hold the switch up manually a few seconds until you hear the slight click to reinitialise the system after a battery disconnection.

Next, the ECU has a built in safety device to stop the operation of the motor if it gets too hot, so waiting a while resolved this.

I’m also wondering if it persistent failing to raise and stay, whether somebody has attempted to replace the regulator wires and got the tensioning wrong when fitting it thus causing the anti pinch to always engage....

[evilclive]

Bad news - new ECU showed new and different faults (air bag fired, but pretensioners fined). So that's going back.
Good news - sent my ECU to crashdatareset and they've cleared the pretensioner warning and it's no longer complaining.

Lack of power might have been sorted by a new MAF. Not entirely sure, since I replaced it and it was still slow for a few miles. The alternative was that the pothole smack kicked the EGR hard enough to drop some soot off it or something similar and get it moving again. Either way it's working now - quite a difference.

Now putting the rear seats back in - trivial, but I've forgotten which order the belt stalks go on. New question for that...