I have just bought an S4 B6 which has an intermittent fault with the airbag warning light coming on part way into a journey. It always seems to come on within 10 minutes of starting out but switching off and on again will clear the light form another 10 minutes. I bought a VAG COM lead and have scanned the car with VCDS Lite and have some codes.
00475 - Control Module for immobilizer
004 - No signal/communication - Intermittent
01794 - Control Module: Incorrect Chassis (VIN) Number
Almost a year ago the car had a new Instrument cluster fitted by Audi - as I have only recently bought the car I don't know if the light has been coming on since then but it does seem a bit of a co-incidence. I'd welcome any suggestions though as to how to clear this problem...