Why would?
 

Why would the check engine light go on in a 95 E320 with just 30K miles? Is it programmed to do that every 30K miles for the 30K miles service intervals?

There are any number of reasons for the light to come on. The only way you will know why it came on is to draw the codes and troubleshoot the problem. If the car only has 30K miles it should be under warranty and should be taken care of by the dealer. If it is out of warranty due to time, it is most likely an emissions issue thus will still be taken care of under warranty.

Good luck,

Do emission warranties go by mileage or by time and mileage or just time? It is a 1995 model.

I just call MB and was informed that emissions warranties are for 8yrs/80K miles. This car wouldn't be covered. But this thing only has 30K miles and has not been driven much at all. In 2003 it had failed emissions and then it was corrected and it has passed emmissions since then. Would the oxygen sensor get bad if the car is not driven much by just sitting?

Time can have just as much of an aging effect on cars as mileage. Did you have the codes pulled?

Its not my car, it belongs to someone else. He was going to take to an indy today. Should know something by tomorrow I think. What codes would be safe? It was driven an average of just 3000 miles per year which comes to about 250 miles / month

Open the hood , push the button, and get the codes

Saerch Function

I'll tell him but he, like me, is mechanically challenged. I think it would be safer for him to take it to a mechanic and have it checked out.

Cool..

Just wanted you to know there is Owner Code access on that model by simply pushing the button in for 2 secs and releasing.. the codes then flash back for the owner so he knows what fault made the computer light the CE lamp .. that tells you exactly what the cars Diagnostic Module thinks the problem is .. and that is more likely correct than the 20 different answers you will get from 20 different guessers.
Pretty user friendly and could save your friend hundred of $$$$$$$$$$$$$$$$$$$ B/4 they are done with him......