BMW NOx Sensor Issues: Repair Costs and Solutions

Hey there! I had a similar issue with my 2009 BMW 3 Series last year. The NOx sensor problem is pretty common with these models. In my case, it turned out to be more than just the sensor, there was a damaged wiring harness that connected to the NOx system, and the catalyst itself was partially clogged. The repair involved replacing both NOx sensors (pre and post catalyst), fixing the wiring harness, and cleaning the catalyst system. It wasn't a quick fix and took a couple of days at the garage. The exhaust leak was actually coming from a cracked flex pipe, which they spotted during inspection. These issues can be tricky because the symptoms often overlap. Don't assume it's just the sensor, my mistake at first. Get a proper diagnostic done. While it was a serious repair job, it wasn't engine-threatening as long as you address it promptly. Worth noting that after the fix, my emissions returned to normal and the check engine light hasn't come back on since.

Thanks so much for sharing your experience! This really helps since it seems quite similar to what I'm going through. Would you mind telling me roughly how much you ended up paying for all those repairs? Also curious if you've had any other related issues pop up since getting it fixed?

Hey again! Great news, my situation ended up being much simpler than I initially thought! While I was worried about multiple issues like in my first post, it actually turned out to be just a loose connection to the NOx sensor. The mechanic found a damaged cable and fixed the plug connection, total bill was only 95 €, which was such a relief compared to what I was expecting! Haven't had a single problem since the repair was done about eight months ago. The check engine light stayed off, and the car's been passing emissions tests with flying colors. Really glad it wasn't anything major like I first suspected with the catalyst or the entire sensor needing replacement. Looking back, I probably worried too much in my first response! Sometimes these BMW sensor issues can be pretty straightforward fixes. Just make sure you get it properly diagnosed, could save you a bunch of money like it did in my case. Let me know how yours turns out! Fingers crossed it's something simple for you too.

What a relief to hear it was such a simple fix for you! I just got back from the mechanic today, and I've got mixed feelings about the whole thing. The good news is they found the issue, turns out I had a faulty NOx sensor and a small crack in the exhaust manifold. The bad news? It cost me quite a bit more than your repair. Ended up paying around 500 for the sensor replacement and another 300 for the exhaust work. But you know what? At least the car's running properly now. The check engine light's finally off, and the weird smell I was getting is gone too. The mechanic seemed pretty knowledgeable and took the time to explain everything, which was a nice change from my last experience. Still, wish I'd had your luck with just a loose connection! But I guess that's how it goes with these older BMWs, you never really know what you're going to get. Thanks again for sharing your experience. It really helped me feel less anxious about getting it checked out.