rolandkoenig93

NOx Storage Catalyst Aging and Exhaust Leak

My 2010 Mercedes SL with a gasoline engine is throwing a check engine light. The codes relate to NOx storage catalyst aging, and I've got 205497 km on the clock. I can also hear a slight exhaust leak. Has anyone dealt with this nitrogen oxides issue before? Is my NOx catalyst shot, or is there something else I should check before replacing parts?

4 comment(s)

Exhaust leaks can definitely impact NOx catalyst efficiency because unmetered air messes with the readings. Inspect the entire exhaust system closely, especially around joints and welds. Is the leak before or after the catalyst? Also, what specific error code are you seeing?

Good point about where the leak is. I'll check that. The error code is P20EE. Does that point to anything more specific than just general NOx catalyst aging? I'm hoping to avoid replacing the catalyst if possible, mainly because of the repair cost.

P20EE confirms NOx catalyst efficiency is below the threshold. The leak is the most likely culprit given your description, so fix that first. If the code persists after repairing the exhaust system, then the catalyst may actually be aged. You'll need to assess air quality impact as well. You may consider a workshop at this point.

Okay, thanks. I crawled under the car and found a cracked weld on one of the exhaust pipes right before the NOx catalyst, exactly as you said. I had it welded up at a local shop for 265€. The code's gone, and the engine light's off. Hopefully, that's the end of it. I appreciate the help.

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