Hi guys, The yellow engine warning light flicked on in our 2004 Sportback 2.0TDI recently and while there were no obvious problems, I took it in to Hatfield Audi this morning to ask them to diagnose it, which they did free of charge while I waited. Unfortunately, I didn't get the full details of the fault because I was expecting to take a copy of the work schedule away with me, and wasn't allowed, but the chap explained that an exhaust sensor or module had failed (he mentioned something about a flap!). I'm sure this isn't an airflow sensor, but the bill would be a whopping £454 - the part alone was a fraction over £245. It takes an hour to fit apparently but I didn't book it in there and then. Does anyone have any idea exactly what this is? As I'm well out of warranty now I'm keen to understand what this might be before getting the dealer to fix it. Any thoughts/comments welcomed.