My service engine light comes on for hte fist five minutes after I start the car reguardless if the car has been running warm or cold start. I have put a new oxygen sensor on about a year ago and have not been able to narrow it down. Any suggestions

On my '90 it is reset by means of a small hole in lower right corner of instrument cluster right below gas gauge. Push a small allen wrench or similiar through when light is lit and it should immediately go out if reset. You can feel the button press in. There is a linkage behind intrument cluster that resets lever behind speedo assembly.

Push in the reset lever behind the dash next to the speedo. This light is not the "Check engine" light that indicates diagnostic codes are set, it only reminds you to service the car at mileage intervals.

This light comes on after 5000 miles on my 1990 240 (US). On the 1990 model there is a little button on the lower right hand side of the instrument cluster. I use a small allen wrench to push it in - it needs to go quite a ways. A bent paper clip also will work. There is some magic sequence, I think that you need to hold it in while you turn on the key - at least this is the sequence that works for me.