BMW 1 NOx Catalyst Failure: Engine Light & Power Loss

Hey there! I've got some experience with BMWs and had a similar issue with my 2020 BMW 2 Series. I feel your pain! Last summer, my engine light came on with the same symptoms, power loss and failed emissions. Took it to my trusted mechanic who found a leak in the exhaust system, right before the catalyst. It was causing similar issues to what you're describing. The repair cost me around 265 Euro and took about a day to fix. What engine variant does your 1 Series have? Also, are you noticing any unusual exhaust sounds or smells? This info would help me understand if you're dealing with the same problem I had. In my case, they had to replace some gaskets and a small section of the exhaust pipe. The catalyst itself was actually fine, it was just the leak causing wrong readings. Would be good to get it checked by a pro before replacing any major parts.

Hey, thanks for sharing your experience! I've got the 2.0L gasoline engine with 109657 km on the clock. Actually, I've been hearing a slight rattling noise from the exhaust area, especially when accelerating. No weird smells though. Had my last service about 2 months ago but these issues started recently. That's interesting about your exhaust leak, definitely cheaper than replacing the whole catalyst! Did your mechanic need any special tools or was it a straightforward fix? I'm hoping mine turns out to be something similar because a full catalyst replacement would be pretty rough on the wallet right now.

Hey again! Thanks for those extra details about your 1 Series. Yeah, that rattling noise definitely rings a bell, had exactly the same thing with my 2 Series before I got it fixed. When my mechanic did the repair, it was pretty straightforward, no fancy tools needed. They used their standard diagnostic equipment to pinpoint the leak location and then just needed basic welding gear for the fix. The most time-consuming part was actually waiting for the exhaust system to cool down completely before they could work on it! Looking back, I probably should've mentioned earlier that before I got it fixed, the rattling on mine got worse over about two weeks. Started just like yours, only during acceleration, but then became more noticeable at idle too. The fact that you're not getting any weird smells is actually a good sign, when my catalyst was working fine but the exhaust was leaking, I didn't get any smells either. My advice would be to get it checked soon though. I waited a bit too long and the leak got slightly bigger, which is why I ended up needing that section of pipe replaced. Could've probably saved some money if I'd done it earlier. Might be worth having them check the gaskets while they're at it, they're usually pretty cheap to replace preventively. Would love to hear what you find out when you get it looked at. Good luck with the fix!

Thanks for all that detailed info! Really helpful to hear about your experience, especially about catching it early. You're right, I shouldn't wait around, I've already called my mechanic and booked it in for next week. The rattling hasn't gotten worse yet, but after what you've said about yours progressing, I definitely don't want to risk it. Makes me feel better knowing your fix was relatively simple and didn't need special tools. I'll make sure to mention to my mechanic about checking those gaskets too while they're at it, good tip about the preventive replacement. Really appreciate you taking the time to share your experience. I'll update once I get the diagnosis and repair done. Fingers crossed it's just an exhaust leak like yours was!