leo_drache1

Mercedes B Klasse NOx Sensor and Exhaust Smell

My 2022 Mercedes B Klasse with a gasoline engine has a persistent check engine light. The reader indicates a NOx sensor failure, and I'm smelling exhaust fumes. The error memory confirms the sensor issue. I checked the sensor's wiring and plug visually, but could a bad connection cause this? A replacement part is quoted at 95€. Has anyone experienced this kind of pollution control sensor failure?

4 comment(s)

NOx sensor failure and exhaust smell, huh? Check engine light is on, so the system definitely sees something wrong. Did you clear the code and see if it comes back? Could be a temporary glitch. If it keeps reappearing, the sensor is likely faulty.

I cleared the code, but it came back almost immediately. The exhaust smell is what's really bugging me, though. If the sensor is failing, would that directly cause an exhaust leak, or are these likely two separate issues?

The sensor itself wouldn't cause a leak. A faulty NOx sensor messes with emission control. The exhaust smell suggests an actual leak somewhere in the system. You might want to get it checked at a workshop.

Appreciate the advice. Turns out you were spot on. Took it to a workshop. The NOx sensor was indeed faulty, and there was a small crack in the exhaust manifold causing the leak. Replaced the sensor and had the manifold welded. Check engine light is gone, and the smell is history. Thanks again.

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