BMW X5 O2 Sensor Issues Causing Rich Fuel Mix?

Hey there! I've got some experience with BMWs, having owned a 2015 BMW X3 3.0i. Had a very similar issue about 2 years ago (medium experience with cars here). The symptoms you're describing sound exactly like what I faced. My check engine was on, and fuel consumption went through the roof. Took it to my regular workshop, and they diagnosed a faulty connection in the O2 sensor wiring harness. The plug had corroded over time, causing intermittent signals. Total repair was 95 Euro, they replaced the connector and cleaned the contacts. Before I can be more specific about your case: Could you share what diagnostic codes you're getting? Also, have you noticed any rough idling or hesitation during acceleration? These details would help determine if you're dealing with the same issue I had. If you want, let me know and I can share my mechanic's exact troubleshooting steps. By the way, I've seen similar issues in other BMWs, including the 5 series, so it's not uncommon in these models.

Thanks for sharing your experience! Yeah, my X5 (87545 KM) is showing pretty much those exact symptoms. The rough idling started about a week ago, especially when the engine is cold. Haven't pulled the codes yet, but planning to do that this weekend using my 's scanner. Had my last service about 3 months ago and everything was fine then. Your repair sounds way more reasonable than what I was expecting, was worried it might be something major. Good to know it could just be a connection issue. Did you notice any performance improvements right after the repair? Definitely interested in those troubleshooting steps if you don't mind sharing them.

Hey again! Yeah, I definitely remember the relief when it turned out to be just a connection issue on my X3. After seeing your mention of the rough cold idle, I'm even more convinced it's similar to what I experienced. Right after the repair, the difference was like night and day. Fuel economy went back to normal within two tanks, and that annoying cold-start rough idle disappeared completely. The engine felt smoother overall, especially during acceleration. About those troubleshooting steps, here's what my mechanic did: First, they checked all the connections around the O2 sensor (found that corroded plug I mentioned). Then they tested the heater circuit resistance, this is crucial because a faulty heater circuit can cause exactly these symptoms. They also checked the sensor's response time using a scan tool. In my case, the sensor itself was actually fine, it was just that corroded connection messing with the signals. But I've seen cases in our BMW forums where the entire sensor needed replacement. Since your X5 has similar mileage to what my X3 had when this happened (mine was around 82000 km), it could be the same issue. Let me know what codes you get from that scanner, it'll help narrow things down. By the way, have you noticed any weird smells from the exhaust? That was another symptom I forgot to mention earlier.

Thanks a lot for those detailed troubleshooting steps and sharing what happened with your X3. Just got back from checking the codes with my 's scanner, getting P0135 and P0141, which apparently point to those O2 sensor heater circuits like you mentioned. And yes! Now that you bring it up, there has been a slightly odd exhaust smell, kind of sweet-ish, especially during cold starts. The similarities between our cases are really encouraging. Think I'll go ahead and book it in with my regular mechanic next week, but feeling much more confident now about what to expect. Really appreciate you taking the time to share all this info. Sounds like I might be looking at a relatively straightforward fix rather than some major engine work, which is a huge relief. I'll definitely update once I get it sorted, might help someone else down the line with the same issue!