BMW i3 NOx Sensor Nightmare, Repair Help Needed

Hey there! I drive a 2015 BMW i8 Hybrid and faced similar symptoms last month. The NOx sensor issue is quite common in these models, but in my case, it turned out to be more than just the sensor. When I brought it in, they found that the wiring harness connecting to the NOx sensor was damaged, causing intermittent signals and false readings. The main symptoms matched yours, failed emissions, check engine light, and catalyst system warnings. The technician had to replace both the wiring harness and the connector assembly. While not the most complex repair, it was definitely something that needed immediate attention to prevent potential damage to the catalyst system. The fix took about half a day in total. It wasn't just a simple sensor swap, they had to trace the wiring path and check for any additional damage. Unlike what most people assume, these issues can be quite serious if left unattended, as they can lead to catalyst system failure. Would recommend getting it checked by a certified BMW technician who specializes in hybrid systems. These symptoms shouldn't be ignored. Hope this helps with your decision.

Thanks for sharing your experience! Glad to hear you got it sorted out. I'm currently looking at repair options and your insight about the wiring harness is super helpful, definitely going to have them check that. Would you mind sharing what the total repair cost was? Also curious if you've had any other issues pop up since the fix? Just trying to budget and plan ahead in case there's more to it than initially thought. Thanks again for the detailed response!

Hey again! Just wanted to follow up and let you know that my repair was actually much simpler (and cheaper!) than I initially thought. After seeing a qualified BMW technician, they discovered it was just a faulty cable connection to the NOx sensor. Total bill came to 95 €, way less painful than I expected! Since getting it fixed last month, everything's been running perfectly smooth. The check engine light is gone, and my emissions readings are back to normal. No other issues have popped up at all. Looking back, I was probably overthinking it when I first posted about the wiring harness, sometimes the simplest explanation is the right one! My advice would be to definitely get it checked out soon, but don't stress too much. These sensors can act up for really basic reasons. Just make sure you go to someone who knows their way around BMW hybrids, it makes all the difference. Let us know how it turns out for you! Always good to share experiences so others can learn from them too.

Just wanted to update everyone on what happened with my i3! Finally took it to a mechanic, and wow, what a rollercoaster that turned out to be. Got there early morning, super nervous about what they'd find. The mechanic seemed pretty confident right from the start, which was reassuring. Turns out, the issue wasn't nearly as bad as I'd feared. They found a loose connection and some dirt buildup around the sensor area. The mechanic cleaned everything thoroughly and secured all connections properly. The whole thing took about two hours, and the bill was surprisingly reasonable, much better than I'd budgeted for! Did a test drive afterward, and the check engine light's completely gone. Passed the emissions test too! No more weird exhaust smells or any other issues. Should've done this weeks ago instead of worrying so much. Really appreciate everyone's input, especially about finding a qualified technician. You were all right, getting someone who knows these hybrid systems made all the difference. What a relief to have this sorted!