Seat Mii NOx Catalyst Issue

The symptoms you describe, particularly the check engine light and exhaust leak, do suggest a potential issue with the emissions system. Has the error code in the memory been read, and if so, what code was stored? This detail would aid in more accurately assessing the situation.

The error code retrieved was P20EE, indicating a malfunction in the NOx storage catalyst. Could this code, in conjunction with the exhaust leak, definitively point to the catalyst aging as opposed to other potential causes?

P20EE in combination with an exhaust leak strongly suggests an issue impacting the NOx storage catalyst efficiency. The leak can cause inaccurate readings and improper function of the catalytic converter, leading to the catalyst aging prematurely. I recommend taking it to a workshop to properly diagnose and repair the exhaust leak and evaluate the health of the catalytic converter.

Acknowledged. The diagnosis of an exhaust leak compromising the emissions system, specifically impacting the NOx storage catalyst, aligns with my findings. I will proceed with the necessary repairs, estimating around 265€. Thank you for your insight.