Problems with black smoke and loss of power in BMW 1 Series (2007): Possible NOx sensor fault

Hello, repair professionals! My BMW 1 Series (built in 2007, gasoline engine) is giving me problems. When I accelerate, black smoke comes out of the exhaust, the indicator light for the engine is on, the performance drops, I can hear a leak in the exhaust system and the exhaust fumes smell bad. Have you experienced anything like this? I suspect a problem with the NOx sensor, but would be grateful for any tips. How did you tackle the problem and what was your experience with the garage? Many thanks for your help!

(Translated from German)

4 comment(s)

Hello, I have a bit of experience with something like this, as I had a similar problem with my BMW 3 Series, model year 2009. Cable connection/connector from the "NOx sensor control unit was defective. It cost me a bit (385 € to be exact), but I had to go through with it. My local garage helped me a lot. Can you tell me how many kilometers your car has done and when it was last serviced? Maybe then I can help you better.

(Translated from German)

Hi, thanks for your reply! Mine now has 124781 km on it. The last service was recently, everything seemed to be in order. But maybe I missed something. Really annoying, but thanks for the tip about the NOx sensor, maybe it's just that.

(Translated from German)

Moin, no problem, you're welcome! I'm no expert, but given the mileage I would definitely have the NOx sensor checked, just as you suspected. I had similar symptoms in my 3 Series at the time and it was the NOx sensor that had to be replaced. The important thing is not to ignore it and visit a garage soon. A problem like this can quickly get worse and then it only gets more expensive. My garage told me at the time that a defective NOx sensor can affect the whole engine, and you certainly don't want to risk that. Oh yes, and the black smoke and strong smell could also indicate a defective catalytic converter. A check in the workshop would also be advisable. In any case, good luck and hopefully it's nothing too bad!

(Translated from German)

Hello, thank you very much for your detailed explanations. It does sound like a lot of work, but I was already worried that it might mean a major repair. I will definitely visit the garage as soon as possible and follow your advice. It's reassuring to hear that I'm not completely wrong in my assumptions. To be honest, I hadn't thought about the catalytic converter before, but it makes sense to have it checked too. I'll get back to you when I know more. Thanks again!

(Translated from German)

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