Mercedes ML Hybrid engine issue resolved

Sounds familiar. I had a similar problem with my old Fiat after filling up at a dodgy gas station. Engine light, rough idling, the whole shebang. Turned out to be water in the fuel tank. Have you considered the fuel quality?

Could you elaborate on the diagnostic process that led to the identification of water contamination in your fuel tank? Was there a specific diagnostic code that indicated this issue, or were there other discernible symptoms beyond the illuminated check engine light and rough idling? Also, did you experience any issues with starting the engine, or any unusual sounds such as an engine knock?

Well, the mechanic suspected it immediately because I mentioned the iffy gas station. He drained a bit of fuel and showed me the water. No special codes, just common sense. It's like when you get bad milk - the car knows something's up. Best bet is to take it to a workshop.

Following your advice, I took my vehicle to a certified Mercedes-Benz technician. After a thorough diagnostic examination, it was determined that a faulty connection was the root cause. The cable connector leading to the fuel composition sensor was corroded, causing intermittent signal disruptions. The repair, including parts and labor, amounted to approximately 95€. The vehicle is now performing optimally.