Dropping Sue's Car off this morning at Mercedes for it's most likely 3rd oxygen sensor in less than 12 months and under 4k miles, covered since the first sensor replacement, hopefully this one is under Mercedes warranty, otherwise a potential £1k bill. Just the investigations alone which is plug into diagnostic tool is £199, refundable if found it is the oxygen sensor.........
If it is like VAG the parts are all guaranteed when fitted and any costs incurred subsequently if they fail early no costs to the end user..
