I had a check engine light come on from the result of a loose gas cap . I had a ex mechanic tell me to pull the battery cable to reset it , the only problem now is the radio doesn't work because it says "code". I have just bought this automobile used and haven't contacted the ex owner yet , I was trying to find out the solution first.

 

You should get the radio-code card from the previous owner. Every Mercedes comes with that card with the radio code on it. You can also try calling 1800 FORMERCEDES, or goto the dealer and ask for the code. I am sure they'll give it to you if you can prove you are the owner of the vehicle