Mercedes R Klasse check engine light NOx sensor issue

A faulty NOx sensor on a Mercedes, especially with exhaust smells, isn't exactly unheard of. The check engine light and stored error definitely point in that direction. Now, you mentioned a possible bad connection, which is where the uncertainty creeps in. While a loose or corroded connector is possible, and would be the cheapest fix, you can't be certain that's the whole story. How did you determine that there might be a bad connection? Did you check the sensor and catalytic converter? Is it a diesel engine?

I haven't actually checked the connection myself. I just read on some forum that a bad connection is a common cause. So, how would I check the connection properly? And does a bad NOx sensor affect the pollution control directly? Also, it is a gasoline engine, not diesel.

Alright, so you're going based on internet wisdom, which is always a gamble. You could visually inspect the connector for obvious corrosion or damage. Wiggle the wires a bit while the engine is running (carefully!), and see if the engine light flickers or the code changes. However, without proper diagnostic tools, you're essentially guessing. And yes, a faulty NOx sensor absolutely impacts your pollution control. It messes with the nitrogen oxide readings, which the engine uses to optimize combustion and reduce emissions, and also the catalytic converter. Honestly, given the symptoms, I'd suggest taking it to a workshop to get a proper diagnosis. They can pinpoint the problem – be it the sensor itself or the wiring – and save you time and potential headaches.

I took it to a mechanic, and you were right – it needed a proper look. Turns out it was just a bad connection on the NOx sensor. They cleaned it up, reconnected it, and cleared the code. Cost me 95€, which is way better than a new sensor! I'm so glad it was a simple fix!