having the same issue as this guy:
(mine is a 2004 2.5 manual 156)
basically, my airbag light would sometimes pop on - but after i jet washed the car (including arches) the VDC failure popped up a few dozen meters from home. This was constant until i cleared it by FES, (which ID the front left sensor as being the issue)... but it popped back up.... recently it would clear itself but then pop back up - it is an intermittent thing now...
thing is - the airbag light cleared itself when FES wouldn't let me.... But it has popped up now and then, but is cleared for now...
Plan of attack:
1) check sensor - i was gunna jack the car and physically inspect the sensor - clean with alcohol, and reseat the connectors make sure all is right.... what is the proper resistence for the sensor to be measured?
2) check battery. off it brings 12.5v, under max lights and radio load - it drops below 12v (IIRC 11.5v), this too little? the car starts under load so i'm on the fence about the battery... car on, alty is bringing around 14.4v at idle, so i'm happy that it doesn't seem to be the alternator...
3) I tried to check the airbag wires in the boot - this is the orange and yellow connector wires at the rear right hand high of the boot i take it - behind the boot trim... they looked in good condition, but i will disconnect and hit with alcohol as well i guess.