BMW X1 Check Engine + High Fuel Use: O2 Sensor Issue?

Hey there! I had nearly identical issues with my 2014 BMW X3 (gas engine) last year. The symptoms matched yours perfectly, check engine light, terrible fuel economy, and failed emissions. Got it diagnosed and yes, it was the O2 sensor heater circuit that went bad. The connector had corroded, causing poor contact. The mechanic found that moisture had gotten into the wiring harness, leading to the connection issues. This wasn't a major repair but definitely not something to ignore. Poor O2 sensor readings mess with the fuel mixture, which explains your fuel consumption problem. The repair involved replacing both the sensor and part of the wiring harness to prevent future issues. My suggestion: get it checked soon. Bad O2 sensor readings can potentially damage your catalytic converter if left too long, and that's definitely not a repair you want to deal with. Hope this helps with your decision.

Thanks for sharing your experience! That's really reassuring to hear since my symptoms match up exactly with what you described. By the way, do you remember roughly how much you ended up paying for the sensor and wiring harness replacement? Also, has everything been running smoothly since the repair? Just want to make sure there weren't any related issues that popped up afterward.

Hey again! Yes, totally, happy to give you the update! You'll be glad to hear that after getting it fixed, my car's been running like a charm. All those annoying symptoms cleared up completely. The mechanic found exactly what I suspected, just a faulty connection to the O2 sensor heater. The total bill came to 95 € to fix the cable connection issue. Pretty reasonable compared to what I was worried it might cost! Much better than having to replace the entire sensor or deal with catalytic converter problems down the line. Since the repair about a year ago, everything's been perfect, fuel consumption is back to normal, no more check engine light, and it passes emissions tests with flying colors. Really, it was one of those repairs that made me wish I'd done it sooner. Just goes to show sometimes these things aren't as scary (or expensive) as we think they'll be. Definitely made the right call getting it sorted quickly. Let me know how yours works out!

Thanks so much for all the details! I actually just got back from the mechanic today, and wow, what a relief! Turns out it was indeed the O2 sensor issue, just like in your case. The mechanic found some corrosion in the wiring, fixed it up, and my car's already feeling much better. I was pleasantly surprised by the cost too, came in right around what you paid. Way less scary than I'd built it up in my head! The fuel consumption has already improved, and that annoying check engine light is finally off. The mechanic even showed me what the corroded part looked like, which was pretty interesting. It's funny how we sometimes put off these repairs because of bad past experiences. This time around, the mechanic was great, really took the time to explain everything and show me what was wrong. Should have done this weeks ago instead of worrying about it! Thanks again for giving me the confidence to get it checked out. Definitely the right call!