So, go back to the dealer with this problem.
I already emailed them. I am inclined to look elsewhere.
If this is an in-warranty repair that was done at no charge by the dealer, then only another M-B dealer will do it at no charge. If this is an out-of-warranty repair and you already paid for it when you got your car back the first time, then you should go back to that dealer and give them another chance to fix it, at no additional charge to you. If they say there is another problem, and you must pay more money then you know to not go there in future. If you are inclined to go elsewhere it will cost you more money for sure.
Here’s a suggestion. I had the check engine light come on in one of our cars (not MB). I took it to my local Indy shop and my friend there checked the gas filler cap and found it to be loose. He put it on tightly, turned out the light and that fixed it. The diagnostic tools showed that was the cause. My tech told me that loose gas caps (and defective one) were the cause of the light coming on in the vast majority of cases
Thanks for the advice. After this I will take it to Prestige Auto Works in Salem Oregon.
31 May 2021 Dear Mercedes Benz Club of America, David Abarr MBCA Portland Section President Legends of the Autobahn Chair Dear Mr. Abarr, I recently moved to Salem Oregon. When my C230’s check engine light came on I made an appointment at the Salem MBZ dealership. Within 24 hours after they “fixed” it, the check engine light was glowing again. They charged me an exorbitant amount for this “service.” I wrote to the Club and you recommended PRESTIGE Auto Works, here in Salem. I am so glad I followed your advice and took my 1998 C230 to Prestige. Not only did they find the faulty vacuum line that was causing my idiot light to glow, they made several other pertinent diagnostic recommendations, based on a thorough exam, documented by extensive photography and explanation. Thank you, David Abarr; and thank you Prestige for helping me with my Mercedes. Sincerely, John G. Bergman