The check engine light only illuminates if there is a fault with any systems relating to smog emissions.
From experience on check engine light problems from posts on this board, it is most likely an O2 sensor or an EGR issue.
Take it to a dealer or an indpendent and get the codes scanned.
2001 E430, Bourdeaux Red, Oyster interior.
1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".