I've read here on this site that there are something like over 20 different systems that can cause a check engine light to come on.
The check engine light is related to smog related equipment.
It can be practically anything, including your transmission.
Do a search under member Arthur Dalton, and he's explained how to retrieve codes via the LED display in your engine compartment. Once you have the code, you'll need to know what the code number actually suggests is wrong.
In any event, check engine light codes seem to be common on these OBD-I cars, and the car will run absolutely fine.
You'll have to clear the code eventually anyway when you need to get your car smogged.
2001 E430, Bourdeaux Red, Oyster interior.
1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".