BMW X5 Check Engine & High Fuel Usage, O2 Sensor Issue?

I had a similar issue with my 2018 BMW X3 last year (I have some experience working on cars, but nothing too fancy). The symptoms were exactly what you're describing, check engine light and terrible fuel economy. Initially, I thought it was the O2 sensor too, but when I took it to my regular workshop, they found it was actually just a loose connection in one of the sensor cables. The plug wasn't making proper contact. Total bill came to 95 Euro for diagnostics and fixing the connection, way better than replacing the whole sensor! Before suggesting anything specific though, could you share: What error code you're getting? How much has your fuel consumption increased? Any other symptoms like rough idling or drop in power? This could help pinpoint if you're dealing with the same issue I had with my X3 or something else entirely.

Thanks for sharing your experience with the X3! My car is currently at 195,640 KM, and I just got it serviced last month. The error code I'm getting is P0171 (System Too Lean Bank 1). Fuel consumption has jumped from about 11L/100km to nearly 16L/100km in the past two weeks. And yes, I've noticed some slight vibration at idle, especially when the engine is cold. I hadn't considered it might just be a loose connection, that's definitely worth checking out before replacing any parts. Was your connection issue easy to spot once they got in there? Did they have to remove anything major to access it? I'm hoping it's something simple like in your case, but I'll get it checked properly just to be safe. Really don't want to risk any long-term damage to the engine.

Hey again! Yeah, when you mention the P0171 code and those specific symptoms, especially the cold idle vibration, it does sound a bit different from what I dealt with on my X3. The lean condition combined with that much increase in fuel consumption (that's quite a jump from 11 to 16L/100km!) suggests it might be more than just a loose connection like I had. In my case, the loose connection was pretty obvious once they got under the hood, it was right at the sensor plug near the exhaust manifold, and they didn't have to remove anything major. But your symptoms sound more serious. Since you've got such high mileage (my X3 only had about 85,000 km when I had my issue), I'd actually lean towards checking the vacuum lines and maybe the mass airflow sensor too. I learned the hard way that these components can deteriorate over time. Had a similar lean code on my previous car that ended up being a cracked vacuum line, super cheap fix but really tricky to spot. Definitely get it checked soon though, running lean isn't great for the engine, as you mentioned. Let me know what they find. I'm curious if it turns out to be something similar to what I've experienced with BMWs before!

Thanks for the detailed response! You're right, those vacuum lines and the mass airflow sensor definitely sound like they need checking, especially given my car's mileage. It's really helpful to hear about your experiences with both the X3 and your previous car. I've already called my mechanic and booked it in for tomorrow morning. They mentioned they'll do a thorough check of all the vacuum lines first, since that's a common issue with these engines at high mileage. Makes total sense after what you've shared. I'll definitely update once I know what's causing the problem. Really appreciate you taking the time to share your experiences, it's given me a much better idea of what to expect and what to ask the mechanic to look at. Thanks again for all the help!

How do you do? I drive a 1 series bmw 118i e87. About my problem, I have replaced both lambda sensors before and after and now have the error lambda control. 002c31. Any ideas? Kind regards.

(Translated from German)

Start by checking for any exhaust leaks before the lambda sensors, as these can cause incorrect readings and trigger the error code. Ensure that the sensors are properly installed and that the wiring connections are secure and undamaged. If the issue persists, it might be worth inspecting the catalytic converter for any blockages or damage. Let me know how it goes or if you have any further questions!