Mercedes A Klasse NOx Issue and Exhaust Leak

My 2019 Mercedes A Klasse gasoline model with 106867 km has the check engine light on, with diagnostics showing NOx storage catalyst aging and a possible exhaust leak. Can a compromised exhaust cause higher NOx and lower fuel efficiency? I think the leak is changing the catalyst's temperature, hurting its ability to reduce NOx.

4 comment(s)

I had something similar with my A Klasse. The check engine light kept coming on. I didn't see a leak, but the car felt sluggish and fuel economy dropped. It could be a simple fix, or something bigger. Have you checked the exhaust for leaks? That's where I'd begin.

Regarding the exhaust leak, did you hear anything, or did you only notice it through diagnostics and performance? I'm trying to figure out how bad the leak is and what it's doing to the NOx system before I get it fixed. Also, do you remember the error code?

Nah, no loud noises. Just the light and worse mileage. I didn't check the error codes, I just took it to a shop. They fixed it fast. With NOx emissions, it's best to let pros handle it. It could be a sensor, but messing with the exhaust yourself is a pain.

I had a technician inspect the car. They found a small exhaust leak, like you thought. The repair, including welding the crack, cost 265€. The check engine light is off, and diagnostics are normal. The leak was affecting the NOx emissions. Thanks for the help.

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