Mini Roadster NOx Catalyst Aging

Greetings. I am sorry to hear about the difficulties you are experiencing with your Mini Roadster. It sounds quite concerning to have the check engine light illuminated and exhaust leakage simultaneously. I had a similar issue with my previous vehicle, a Volvo, in relation to NOx emissions. The engine light appeared and the car had difficulty accelerating. Upon inspection, it was revealed that a faulty oxygen sensor was the root cause of the problem, leading to an imbalance in the air-fuel mixture and subsequently affecting the NOx catalyst's efficiency. Have you checked the oxygen sensors? This might be the source of the problem.

Interesting, thanks for the insight. I had the error codes read, and it specifically mentions the NOx catalyst aging, alongside a general 'exhaust leak' code. Would a faulty O2 sensor directly trigger the NOx catalyst aging code, or is it more likely the leak messing with the sensor readings?

Considering the information you have provided, it appears that the exhaust leak is indeed the more probable cause of the NOx catalyst aging error. The leak would disrupt the proper functioning of the catalyst by allowing unmetered air into the system, leading to incorrect readings from the oxygen sensors and ultimately affecting the catalyst's efficiency. Given that you've already identified a potential exhaust leak and received a corresponding error code, I would strongly advise taking your Mini to a qualified automotive repair shop for a thorough inspection and repair of the exhaust system. It is important to address this issue promptly to prevent further damage to the NOx catalyst and to ensure compliance with emissions standards.

Just wanted to close the loop on this. Turns out it was a small crack in the exhaust manifold, right before the NOx catalyst. They welded it up, cleared the error, and everything seems fine now. Cost me 265€ all in. Thanks for the advice, it pointed me in the right direction.