BMW XM Engine Light & Power Loss: NOx Catalyst Issues?

Hey there! I have some experience with BMWs and had a similar issue with my 2021 BMW X6. I totally get your concern about the power loss and emissions problems. I actually faced almost identical symptoms, engine light, power drop, and failed emissions. Turned out there was a leak in the exhaust system right before the catalyst. The workshop discovered it during a pressure test. They had to replace a section of the exhaust pipe and some gaskets. The whole thing cost me around 265 Euro, and it fixed the issue completely. Before I give more specific advice, could you share: Have you noticed any unusual exhaust sounds? Does the power loss happen gradually or suddenly? How many miles/kilometers has your XM done? My X6 had around 45k miles when this happened, and knowing your mileage would help compare situations better. Having dealt with a couple of BMWs, these symptoms definitely sound familiar, but let's get more details to be sure we're looking at the same problem.

Thanks for sharing your experience! Mine has 68322 KM on the clock, and yes, I've noticed a distinct rattling sound from the exhaust area, especially when cold. The power loss tends to come on gradually, usually getting worse after the engine warms up. I had my last service about three months ago, and everything was fine then. The symptoms you described with your X6 sound really similar to what I'm experiencing. Did you notice any specific conditions when the power loss was more noticeable? For me, it seems worse during acceleration. I'm planning to take it to the workshop next week, but it's reassuring to hear your issue was resolved without major complications.

Hey again! Thanks for those extra details. Yeah, that rattling sound is exactly what I had with my X6 too! And what you're describing about the power loss during acceleration, I experienced the same thing, especially when trying to overtake on highways. After my last reply, I remembered something important I should mention. In my case, the power loss actually got worse over about two weeks before I had it fixed. Started off barely noticeable but got pretty bad. The rattling noise also got louder over time, which was a clear sign something wasn't right. One thing I learned from my experience, if you're taking it to the workshop next week, try to drive it gently until then. I made the mistake of pushing my X6 a bit too hard when these symptoms first showed up, and it probably made things worse. The mileage on your XM is pretty similar to what mine was when this happened. Given how similar our symptoms are, I'm betting you're dealing with the same exhaust leak issue I had. The good news is that it's totally fixable and, like I mentioned before, wasn't too expensive compared to what I initially feared. Let us know what the workshop says, would be really interesting to see if it's the same problem I had with my X6!

Thank you so much for all the detailed information and sharing your X6 experience. Your advice about driving gently until the workshop appointment really makes sense, I'll definitely keep that in mind. It's particularly reassuring to hear that your issue was resolved without breaking the bank. After reading about your experience and the similar symptoms, I'm feeling more confident about what might be wrong with my XM. I've already scaled back on highway driving and have been taking it easy on acceleration, just to be safe. The rattling has gotten slightly more noticeable in the past few days, so your advice about not waiting too long seems spot-on. I'll definitely update the thread after my workshop visit next week. Really appreciate everyone's help and insights, especially about the potential exhaust leak. Having some idea of what to expect is making me feel much better about the whole situation. Thanks again for taking the time to share your experience and advice!