Z4 O2 Sensor Woes: Check Engine Light & Poor MPG

Hey there! I had a really similar issue with my 2018 BMW M2 last year. The check engine light and poor fuel economy turned out to be exactly what you're suspecting, an O2 sensor problem. In my case, it was actually the wiring connector that had corroded and lost proper contact with the sensor. Had it fixed at a certified shop where they first did a thorough diagnostic. They found that moisture had gotten into the connector housing, causing intermittent connection issues. They replaced the entire wiring harness section and the connector. It wasn't a major repair, but it needed to be done right to prevent future issues. Just want to mention, this type of problem won't go away on its own and could potentially cause damage to your catalytic converter if left unchecked. I'd suggest getting it looked at soon by someone who really knows BMWs. Check engine light and poor fuel economy is a classic sign of O2 sensor issues on these cars. Best of luck with the repair.

Hey, thanks so much for sharing your experience! That's super helpful to know it was a wiring connector issue in your case. I'm actually planning to take mine in next week to get it sorted. Just curious, do you remember roughly how much you ended up paying for the whole repair? Also, has everything been running smoothly since the fix, or have you noticed any other quirks pop up? Really appreciate your help with this!

Hey again! Glad to give you an update! After I took my M2 to the shop, they found and fixed the aged oxygen sensor, it was exactly what they suspected from the error code. The repair cost me 95 € total to fix the faulty cable and plug connection. Pretty reasonable considering what I was worried it might be! The car's been running like a dream since then, fuel economy is back to normal and that pesky check engine light hasn't shown its face again. No other issues have popped up either, which is fantastic. It's been about a year now, and honestly, it was totally worth getting it sorted quickly. The key was having someone who really knew what they were doing with BMWs. These sensors are pretty common issues on our cars, but once they're fixed properly, they usually stay fixed. Hope your repair goes just as smoothly as mine did! Let me know how it turns out.

Thanks for all that info! Just got back from the mechanic today actually. You were spot on about getting it done quickly, turned out my issue was pretty similar to yours. The mechanic found a faulty O2 sensor wiring connection too, but in my case, they had to replace the entire sensor since it was showing signs of wear. The whole thing cost a bit more than yours, around 150 bucks, but honestly, I'm just relieved it's fixed. Took the car for a drive afterward and could immediately tell the difference, engine's running smoother, and the fuel gauge isn't dropping as fast as it was before. Best part? That annoying check engine light is finally off! Really appreciate you sharing your experience, helped me feel more confident about getting it checked out. Think I've found my new go-to mechanic too. They were super transparent about everything and even showed me the old sensor. Definitely won't be so nervous about future repairs now!