This is a broken/stuck evap vent valve, This valve is open with the engine off and provides an air relief for the tank while filling up.

get under the car and look near the filler neck - there should be a wide tube/hose going to a box looking thing with an electric connector. Remove that unit and clean the valve with some WD40 and make sure the venting filter/tube is clean.

It will fix this problem. This entire system is not unique to Mercedes Benz, its part of a US mandate for all cars that run on public roads in USA.

Look up the generic code on the web, you will find it a problematic issue on american cars and those sites will have good diagrams and procedures on how to test and repair this system.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)