BMW i3 O2 Sensor Issues, High Fuel Use Warning Signs

Hey! I've got some experience with hybrids, nothing too fancy but I've learned a bit over the years. I had a similar issue with my 2016 BMW i8 (actually considered the i3 too). Got those same symptoms, check engine light, wonky readings, and burning more fuel than usual. Took it to my regular workshop and turned out it was just a loose connection in the wiring harness near the oxygen sensor. Total bill came to 95 Euro, mainly labor costs for tracking down the issue and fixing the connection. Much better than replacing the whole sensor! Quick question though, what error codes are you getting specifically? That would help narrow things down. Also, when did you first notice the increased fuel consumption? This info would help figure out if you're dealing with the same problem I had. If you want, share those details and I'll tell you more about what my mechanic checked during the diagnosis.

Thanks for sharing your experience! I've got 90897 KM on my i3, just had the last service done 3 months ago. Those loose connection issues you mentioned sound quite similar to what I'm experiencing. Getting P0135 and P0141 codes, and started noticing the fuel consumption increase about two weeks ago. It's consuming roughly 15% more than usual now. Think I'll follow your advice and have them check the wiring first before jumping straight to sensor replacement. Could save me a decent chunk of change! Did your mechanic mention how long the diagnosis process typically takes? Planning to book it in next week.

Hey again! Yes, those P0135 and P0141 codes do sound really familiar, they're exactly what my i8 was showing. When I got those codes, my mechanic spent about 2-3 hours doing a full diagnostic check. The wiring issue was tucked away pretty good in my case, but once they found it, the fix was pretty quick. Given your mileage and the fact that the symptoms started suddenly after a recent service, I'm even more convinced it could be a connection issue like mine was. When they were working on my car, they found that some of the connectors had worked loose over time, and the recent maintenance might have jostled things around a bit. Just a heads up though, while checking the wiring, have them look at the heater circuit too. That was actually part of my problem, and these codes can sometimes point to that. My fuel consumption went back to normal pretty much right after they fixed the connection. The funny thing is, I was also ready to shell out for a new sensor before finding out it was just a loose connection. Definitely saved me some money there! Let me know how it goes when you get it checked out, curious to see if it's the same issue.

Thanks so much for all the detailed info! That's really helpful about the heater circuit too, I wouldn't have thought to mention that to the mechanic. I'll definitely make sure they take a good look at it. Just booked the car in for next Tuesday morning. The service advisor mentioned they should have it diagnosed within the day, which sounds about right based on your experience. Really hoping it turns out to be just a connection issue like yours, fingers crossed! I appreciate you taking the time to share your experience. You've saved me from potentially jumping straight to replacing parts unnecessarily. Will let you know how it goes after the checkup!

I have the error code 002A99, it says crankshaft, exhaust camshaft. I have changed the lambda probe sensors as it says in the app but the error is still there. What else can I do?

(Translated from German)

Start by checking the timing chain and its tensioner, as a misalignment can cause the 002A99 error. If the chain is loose or worn, it might need adjustment or replacement. This issue can affect engine performance and should be addressed promptly. Let me know how it goes or if you have any further questions!