BMW Diesel Power Loss + Failed Emissions: Expert Help?

Hi there! I actually faced similar issues with my 2012 BMW 5 Series diesel last winter. The symptoms match exactly what you're describing, power loss, check engine light, and failed emissions test. In my case, it turned out to be a cracked exhaust manifold and a failing NOx catalyst. The exhaust leak was causing the system to pull in extra air, throwing off the emissions readings and triggering the engine management system to reduce power. Had it fixed at the garage, and it was quite a serious job, took them two days to complete. They had to replace both the manifold and the catalyst. The engine's running perfectly now, no more leaks or power issues, and it passed the emissions test with no problem. I'd definitely get it checked soon though, running with an exhaust leak can cause more damage to other components over time. Make sure to find a garage that specializes in BMW diesels, as these systems are pretty complex. Hope this helps with your decision making.

Hey, thanks for sharing your experience! I went through pretty much the same thing with my BMW. Really glad to hear you got it sorted out. I'm actually curious, do you remember roughly how much you ended up paying for the whole repair? Also, has everything been running smoothly since then, or have you noticed any other issues pop up? Mine's been doing fine after the fix, but always good to know what to watch out for.

Hey again! Yes, happy to share the follow-up! Since seeing the mechanic last winter, everything's been running perfectly. They fixed the NOx storage catalyst aging issue and found a leak in the exhaust system. The whole thing cost me 265 €, much less than I initially feared. My 5 Series has been performing like a champ since the repair. Power's back to normal, no more check engine light, and she's passing emissions tests with flying colors. I've put quite a few miles on it since then without any related problems popping up. The exhaust note is back to normal too, no more of that annoying leak sound. Really glad I got it sorted when I did, as the mechanic mentioned it could've caused more expensive problems if left unchecked. Just keep an eye on your exhaust note and power delivery, if anything changes, get it checked right away. But honestly, once these issues are properly fixed, they tend to stay fixed. Mine's been rock solid since.

Thanks for the detailed follow-up! I actually just got back from my mechanic today after dealing with my BMW's issues. What a relief, turns out my repair was similar but cost a bit more, around 400 bucks. They found a cracked exhaust pipe along with the catalyst problem, which explained all those weird noises I was hearing. I'm pretty happy with how everything turned out. The car's running way better now, no more power loss, and that annoying check engine light is finally gone. It's like driving a different car! Had to go through three mechanics to find someone I trusted, but it was worth the hassle. Really appreciate you sharing your experience, it helped me know what to expect and not get ripped off. Fingers crossed both our BMWs keep running smoothly from here on out!