Check Engine Light on...now what?

[bboyer32]

I own a 1995 SL320, with 40,000 miles on it. The check engine light came one. The manual says it means either an emissions or a fuel injection problem. The car drives fine, so I assume it's not fuel injection. In relation to emissions (if that's what is), could it just be a sensor? Would a catalytic converter failure cause this?

Any input would be helpful!