hardwick, make sure the gas cap is on firmly. Now how are you resetting the light to go off. Do have access to an impulse counter or trouble shooting diagnosing tool. It could be many things. Lately Ive seen since the new fuels thats out there casuing the 02 sensor to go bad. The new fuels burn alomost to lean at time causing premature failure of the oxygen sensor to go defective do to over heating and runing to lean,which is caused by the oxygenated fuels. Im just telling you what I see alot happening.

But first thing first find out and extract the code.
keep me posted



GUIDO
FACTORY TECH MERCEDES BENZ 14 YRS
1993 500E