Airbag error

cavaddict

MOT time again and it's failed on the airbag light being on. Bunged on Opcom and have faults 77 & 87 drivers side and passenger side airbag squib resistance too high. Both are at 690 which is weird in itself as it looks like all the circuits from the ECU are independent. Have changed the ECU twice so don't think it's that. Any ideas?

MikeS

messed about with seats recently ?

cavaddict

Nope. Just to check, I've lifted the passenger seat, undone the airbag wire, still the same fault. So, I shorted the plug to give a direct link, still the same fault of high resistance. Stumped. Looking at a wiring fault somewhere methinks.

MikeS

you changed the airbag on the driverside ?

cavaddict

Nope. Nothing has been done to the car for at least a year except servicing. Light just didn't go off one day. Just going through TIS for some fault finding and will test all the airbags and retrospective connections tomorrow. Fingers crossed for dry weather lol.

Daz

shorting the plug isnt a great idea..

cavaddict

Well worst case it'll give me a low resistance error, but as it is, it's making no difference so I'm guessing I have some wiring issues.

MikeS

they run off the same circuit m8

i know for fact that if the seat tensioners fail they set off dtc for the other airbags

cavaddict

Hmm, will check the wiring there first. The diagram on TIS shows all separate circuits, but, that's not to say there isn't common links in the ECU. Is a weird one. Think I have some spare seats somewhere too, so might just be easier to bung them in and see what happens.

Daz

New mot rules are gonna cost some peeps a small fortune for airbag lights on ....

Take clocks out and do summat with the bulb, for the mot. then fix at ure leisure when its passed

MikeS

i know someone who fitted new seats in an astra

showed up dtc for both airbags, didnt matter if the codes were cleared they were on permanently, i put it down to dodgy wiring

easy thing to do is find the threshold resistance and buy a resistor from maplin :p

but that is of course unsafe

cavaddict

Lol, resistance should be 2ohm I believe, will change the seats to see if it clears the fault, then swap them over individually to try and locate the fault.

vocky

use some 2.7 Ohm resistors instead :whistle:

cavaddict

Plot thickens! Seems I have no continuity across connector X1. The big green one in the passenger footwell. When it stops snowing I guess I'll be stripping that out too then :-)

cavaddict

Now this is getting really weird. Found a broken wire into X1. Fixed it and cleared the codes. But I still have the light on.

cavaddict

Sorted. The broken wire had shorted on the metal trim panel screw that's welded to the car. Think this has damaged the original ecu. Put another in it, cleared the faults again and viola!!!

vocky

sorted 😃

MikeS

aye told ya it is wiring