While away in Amsterdam for the weekend, I left my S4 with Sinclair Audi, Swansea, for a service. Just got home to find the receipt for £250 and a list of error codes thrown up by the engine management. Can anyone shed some light on these? 3 fault / notes detected 16538 Po154 035 O2 sensor circuit, bank2-Sensor1 no activity detected 17536 P1128 035 Bank1, mixture adaption ( Mult) system too lean 17528 P1120 035 Bank2-probe1, heating circuit open circuit Audi told me if I have problems with the performance, let them know and they will check if the errors, which they cleared, have returned before finding out what is wrong. Anyone else had these problems? If so, what caused it and how much does it cost to fix? Cheers.