Presage NOx Catalyst Error Exhaust Leak

I had something similar with my 2012 Audi A6 diesel. Check engine light, diagnostic said catalyst inefficiency. Turned out to be an exhaust leak from a fractured flex pipe. Is your leak before or after the catalytic converter?

The leak seems to be near the catalytic converter, maybe a corroded weld or flange. Could a leak there cause the NOx storage catalyst to age prematurely, like the error code says?

Yes, a leak that close to the catalyst will mess up the air/fuel ratio needed for NOx conversion. The ECU will try to compensate, which stresses the catalyst and can lead to failure. I'd suggest a good workshop for thorough diagnostics, it can be tricky to find the exact leak location and damage.

Thanks, I took it to a certified shop as suggested. They found a big leak at the catalytic converter flange. They welded the flange, replaced some corroded bolts, and it cost 265€. The error code is gone, and the check engine light hasn't come back.