Hi all, I own a a3 1.6 (poor engine, I know) 8v 52 plate with 76k on the clock! I have a engine management light on! I took it to the garage and the diagnostics said one fault only which was the O2 sensor ONE. He reset the computer than 2 days later the same thing! Which O2 sensor is that pre cat or past cat? I am also hoping to do a full oil change next week, as the previous owner didn't look after it and hasn't had it serviced in years. (I have also done air/pollen filters etc) I will be changing the filter, and cleaning and scrubbing the sump also. I have vw audi sealent for the sump as I am aware they prefer to use sealent and not the gasket itself? Is there anything Else I should be taking a look at/cleaning while the sump is off? Many thanks!