BMW i8 NOx Sensor Issues: Multiple Warning Signs Appear

Hey there! I have some experience working on hybrids. I had a similar issue with my 2016 BMW i3 (another electrified BMW). The symptoms were pretty much identical, check engine light, emissions problems, the works. Turned out it was indeed a loose connection in the NOx sensor wiring. My local workshop spotted it during diagnostics, and they had to replace some corroded cables and clean the connector. Total bill came to 95 Euro, and it fixed everything. Before you dive into repairs, could you share: Any specific error codes you're getting? Have you noticed any changes in fuel consumption? Does the issue happen more when the engine is cold or warm? These details would help determine if you're dealing with the same problem I had. The i8 and i3 share some similar components in their hybrid systems, so I might be able to give you more specific advice.

Thanks for sharing your i3 experience! Actually, my situation might be a bit different since my i8 just had its latest service about 2 months ago. I've got 24783 KM on the clock, and I'm seeing consistent fuel consumption increase. The error codes are pretty irregular, they seem to pop up mainly when the engine's warm, especially during longer drives. The exhaust leak noise is quite noticeable too, which wasn't mentioned in your case. Has anyone else experienced these specific symptoms with warm engine operation? It's starting to get a bit concerning since it's my daily driver.

Hey again! Yeah, now that you mention the warm engine issues and that exhaust leak noise, I'm thinking your i8's problem might be different from what I experienced with my i3. In my case, the NOx sensor issue was pretty straightforward, just wiring problems. But with what you're describing, especially that exhaust leak and the timing of when it occurs, I'm leaning towards thinking you might have a more complex issue. After I posted my previous reply, I actually remembered that my 's i8 had similar symptoms, warm engine problems and all, and it turned out to be a cracked exhaust manifold, not just a sensor issue. The increased fuel consumption you're seeing is particularly interesting because that's something I didn't experience with my sensor problem. Have you noticed any performance changes? Like hesitation or power loss when the engine's fully warmed up? I'd definitely suggest getting that exhaust leak checked out first. The timing of the issues (during warm operation) and the noise make me think it could be affecting your NOx readings and causing those regeneration problems. Might be worth having your workshop take a look at the exhaust manifold and connections, could save you from chasing sensor ghosts like I initially did with my car. Let me know what you find out. I'm really curious if it turns out to be similar to my 's manifold issue.

I appreciate your detailed response and connecting me with your 's similar i8 experience. Yes, now that you mention it, I am noticing some slight power hesitation when the engine's fully warmed up, especially when accelerating hard. The performance isn't as crisp as it used to be. You're probably right about checking the exhaust manifold first, that seems to align better with all my symptoms compared to just a sensor issue. I'll schedule an appointment to have the workshop specifically inspect the exhaust manifold and connections. They did miss checking that during my service two months ago, focusing mainly on routine maintenance items. I just hope it won't be too expensive of a fix, but better to address it now before it causes more problems. Thanks for the helpful advice! I'll update once I find out what's actually causing all these issues. Really appreciate you taking the time to share both your i3 experience and your 's i8 story, it's given me a much clearer direction on what to investigate.