As you have found the check engine lamp is to monitor EMISSION related problems only! Have a trusted (trained) technician with scan tool retrieve codes from computer. The dealer at HH was incorrect!! 1995 cars do not have any monitor for gas cap being removed w/driving. Most all cars starting w/1997 do have monitor (V-8 & V12 cars in 1996). Don't spend $$$ until computer is tested.
MERCEDES BENZ MASTER GUILD TECHNICIAN
ASE MASTER TECHNICIAN
27 YEARS DEALER M.B. Shopforeman
190E 2.3 ITS RACECAR
1986 190E 16V