A couple of days ago, I had to drive only 6-7 miles, but it was the rush hour and the traffic was beyond appalling. So I spent a lot of time standing still. When I got in the car later to come back, the MIL came on.
Yesterday I went to my (independent) garage, and the fault readout was that it was related to the oxygen sensor. Later on yesterday, I had a chance to drive a bit faster than the last couple of days - ony 50 or so - and I noticed the light went off again!
So, could all the idling have done something to the sensor, which was later undone when I got the chance to drive faster? Anyone come across this before?