2018 E300 Check Engine Light - P0301 and Rough Idle

ClearTheCode guidance (Mercedes-Benz · Diagnostics & codes)

Summary: For 2018 E300 Check Engine Light - P0301 and Rough Idle, work through these steps on your 2016+ vehicle:

1. Confirm the symptom — note when it happens (cold start, highway, after fuel fill, etc.).
2. Scan codes — save all pending/stored DTCs; don't clear until you've recorded them.
3. Check TSBs & recalls — look up your VIN for open campaigns and known fixes.
4. Inspect the obvious — related fuses, connectors, fluid level, and recent repairs.
5. Test the common fix — follow model-specific service procedures; one change at a time.
6. Escalate if needed — burning smell, no brakes, overheating, or stalling in traffic → shop visit.

Owner reported: My 2018 Mercedes-Benz E300 (W213) just threw a Check Engine Light this morning. I scanned it with my OBD-II tool, and it's showing P0301, which is a Cylinder 1 Misfire.

The car feels a bit rough at idle, almost like it's shaking slightly, but it drives okay once I get going. I've heard this could be anything from a spark plug to an injector.

What's the best way to start diagnosing this myself b…

This is educational guidance, not a substitute for hands-on diagnosis.