2002 Citroen Xsara Airbag light help - Off!

[beko1987]

Hi! I've got a problem with by beloved Xsara, the airbag light is solid on every time the car starts, with a warning beep! 2002 Phase 2 Hdi 110 with multiplexed wiring

It started leaving work one day out of the blue. I've gone through the seat connectors and checked they have good contact/bent the pins about midly to ensure good contact. Also I did upset the seat connector one (my 11 year old drove the car in a private field so the seat was right forward then I put it right back to drive). The light flashed then, rather than be solid.

Someone from the Autoshite forum then kindly came by with his Lexia setup (Lexia modern full chip clone he said, he uses it on his 306). The lexia connected to my car fine, and read every module on the car bar the air bag module. It couldn't connect to that...

Lots of other faults got cleared and we confirmed my suspicions of a dodgy MAF sensor and after a clean and clearing all the codes the car has never run so good but.... the airbag light is still on. The fact a known OK lexia setup couldn't connect to the airbag ecu is suspect, but I am now stumped on where to start. My initial thoughts are to have a good look at the fusebox and wires under the steering wheel incase one has snapped, but that will be like looking for a needle in a haystack! Has anyone encountered this before? MOT is not long away and she'd have a clean pass otherwise

[wheeler]

Did you happen to note if there were fault codes in the switch module at steering wheel (Com200) & BSI relating to communication with airbag ECU?
If you are confident the diag tool is not the issue then you really need to check that the airbag ECU has all its power supplies & Earth.
This should be the diagram below.
Looks like pin 34 is earth, Pin 47 is ignition live & pin 37 is the VAN+ supply, this should be live with 12v whenever the network is awake. To confirm the ECU is dead you would also need to scope the CAN lines at pins 30 & 33.
I would only advise doing this if you are confident what you are doing & verify all the wiring codes to make sure the numbers tie up with the diagram.

[beko1987]

Thanks, that's a great help!
I'm a 3/10 on the probing confidence scale tbh, especially with the airbags...
My rough plan next is to have a good look (contorted up in the footwell) at the wiring going from the fuse box across to the airbag ecu and check nothings rubbed through or similar... I'd also like to check the earth's to the unit incase something else has shorted and the grounds are messed up. I've not even given the fuses a good look yet but I doubt it's that simple...

I got to here yesterday and confirmed the unit wasn't covered in corrosion or etc.

The guy did say he was happy to lend me his setup for further use, which I might take up...
You don't happen to have a diagram for the fuse box circuits do you? I'd be nervous probing the wires with the battery connected, but if I know where they might run to I can point to point the wire without power to the rest of the car

[wheeler]

The ignition live feed is unfused, the VAN+ supply will be fused but if that was fused i would suspect you’d have other issues.

[beko1987]

Yes that's why I'm not going to do more than a quick check, everything else works*


*nothing new has broken

If its not an obvious connection issue I'll have to try and borrow mateys lexia again

[beko1987]

F*ck me it's gone I don't know what I did either
I took the main earths from the airbag ecu off (all looked fine) and put them back on, fiddled with the fuse box and dropped the bsi down, got scared and put it all back. Drivers airbag out, not disconnected but I poked at the plugs with my finger. Went to the skate park, came back, did lunch then I went under the passenger side of the dash, had all 4 of the big multiplugs (which are all covered in that foamy sticky s**t) apart, blast of contact cleaner and back together.

Tidied up the car feeling deflated as I'd not found anything, fired it up from outside the car incase the airbag did explode and THERE WAS NO BEEP! Drove up the road and back and it didn't come back on... I wonder what's causing that

My windscreen scuttle plastics have never been the best (I've sealed it up a bit recently), and I did flex the bsi a bit refitting it... I'm wondering if I've got lurking bsi issues, is it a big job to unplug it, clean and check the pcb and refit it? All seemed very jammed up in there.

Will see how it behaves on my way to work Tuesday!

[beko1987]

Handily, it stayed off for the mot! So it has a clean pass with zero advisories. Which is good as the other day the light came back on

I'm fairly certain that me manhandling the bsi flexed it in some way, which make some think there could be an issue with it. Does anyone know the best way to fully unplug and remove it from the car? It seemed quite tricky last time, although I didn't unplug anything which probably didn't help. If I could get it out and open it up I could check for water damage, dry solder joints etc and at least start somewhere.

Shame really as otherwise the the car drives beautifully atm! No knocks or bad noises, no smoke from the exhaust, clutch is good etc. Otherwise in August 205 I'll flex the bsi once more... But that doesn't fix the problem