hi mate had this on my car
took it for diagnosis they said lamba sensor was on its way out they reset the diagnostics on the car and it was fine for about 3 weeks then it came back on
in the end i coughed up the money for a new sensor and had it done its now been 2 weeks and its still off hoping it dosent come on again i believe it was 60-70 quid for sensor roughly 15-20 for labour and 30 quid for original diagnosis
best bet is take it to sum1 with a diagnosis machine usaully costs 30-35 squid to put it on there but itll give the garage some codes and these will tell them whats up with your car then your mind can be at rest
u never know it could be summin more serious but half the time its the lamba sensor as the guy above said also they sometimes go out by there selves but my car was newish to me and i wanted to get it sorted
nice1 mate