Mercedes Viano check engine light and nitrogen oxide sensor problem

I had a similar issue with my Vito. The nitrogen oxide sensor went bad. The check engine light was on and the air-fuel ratio was off. Sometimes it can be related to pollution control issues. Have you checked the sensor cable and plug? A defective cable or plug connection can cause the emission sensor to fail.

When you say cable and plug, are you talking about the NOx sensor itself, or is there another connection point I should be looking at?

Yes, I mean the connection to the nitrogen oxide sensor itself. It's worth checking before you assume the sensor is completely dead. However, if it is indeed the sensor, it might be best to have it checked by a workshop, especially with the exhaust leak.

Thanks for the advice. Turns out the cable was indeed faulty, just like you said. Replaced it for 95€ and that fixed the nitrogen oxide sensor issue. I appreciate the help!