martha_star1
Mercedes A Klasse NOx Issue and Exhaust Leak
Summary of the thread
A 2019 Mercedes A Klasse had a check engine light due to NOx storage catalyst aging and a potential exhaust leak. The owner suspected that the exhaust leak was altering the catalyst's temperature, impairing its NOx reduction capability and affecting fuel efficiency. After a technician confirmed a small exhaust leak and repaired it, the check engine light turned off, and diagnostics returned to normal, indicating the leak was impacting NOx emissions.
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4 comment(s)
martha_star1 (community.author)
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?
janamystic2
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.
martha_star1 (community.author)
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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MERCEDES
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AKLASSE
janamystic2
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.