OK, this is not intended as a definitive fix thread but covers probably the most common cause of the airbag warning light displaying on the dash. I'll try to be as accurate as I can and hopefully the pics are clear enough for most to understand.
Due to new regulations (in the UK) cars with an illuminated airbag warning light will fail the annual MOT test. A lot of people worry that this is going to be an expensive fix and I've heard some garages are charging for new airbag units rather than checking the known common faults.
First things first. Disconnect your battery and leave it for at least 15 minutes (make sure you have your radio code though).
Next up you will need a few basic tools available from many DIY stores. Servisol Super 10 electrical contact cleaner/lubricant, some small cable ties, some wire cutters/pliars. it would also be handy to have a copy of Multiecuscan installed on your laptop and a set of cables.
Right, find the yellow connector under the passenger seat, there's usually a cover over it. remove the cover to expose the connector..
seperate the connector (careful not to break the clips), give it a short blast with Servisol/contact cleaner and reconnect. Then secure the connector together using a cable tie...
In most cases this is often enough, but in some instances the issue may be with one of the two connectors in the boot. They can be found on the drivers side (UK/Austrailia) under the lining roughly behind the fuel filler area...
repeat the above proceedure and replace the boot lining.
reconnect the battery (you do have the radio code don't you!) and start your car, the light should now be extinguished.
Some older models (pre-2004) may require the code to erased/reset, this can be done with Multiecuscan/alfadiag and the correct interface
Multiecuscan - Diagnostics software for Italian cars (Powered by FiatECUScan)
one of these cables will work:
or contact Rarebear on here for one of his.
follow the multiscan setup instructions and connect to your car via the diagnostics port which is located in the fusebox...
select your model from the list and connect to the airbag module. navigate to errors and you will see the stored codes, hit erase and hopefully that should be all you need to do...
I hope this makes sense...