Check engine light - 1990 760 turbo sedan

[kentfather]

check engine light - 1990 760 turbo sedan. I just had a reduction in engine power (near stall) -- and check engine light came on. I can find nothing wrong with my engine cooling or oil level. I parked car for a while to cool. Then I started again -- and car runs fine, but check engine light is still on. I have had some rattle from bottom for a while. Would this problem probably be a catalytic converter, or what. Can/should I drive it as long as it is running okay. I am looking for another car anyway.