GLE NOx Sensor and Exhaust Smell

A NOx sensor failing on a GLE with that mileage is unfortunate, but not unheard of. The NOx sensor is part of the exhaust system and crucial for monitoring the air-fuel ratio, so a faulty one could contribute to an exhaust smell, especially if it's causing the system to run rich or lean. However, a physical leak is another matter entirely. Is the smell constant, or does it only appear at certain times, like during startup? Are those cable/plug errors directly related to the NOx sensor circuit specifically? What are the exact error codes? That sensor failure can affect the catalytic converter, and vice versa, so pinpointing the root cause is key.

The exhaust smell seems most noticeable when the engine is cold, disappearing a bit once it warms up. I thought I'd inspected all the connections, but maybe I missed something. The error code I saw was related to the NOx sensor, but I'm not sure about the catalytic converter. Should I replace the NOx sensor, or am I looking at a bigger problem with the converter?

Okay, exhaust smell when cold could point to a cracked manifold or gasket issue, completely separate from the NOx sensor. However, since you're getting codes directly implicating the NOx sensor and the smell diminishes when warm, it's still highly probable the sensor is the primary culprit. But here is the thing, a bad NOx sensor can damage the catalytic converter over time. Considering the age and mileage, and the fact that you're getting electrical connection errors alongside the sensor failure, I would say visiting a trusted mechanic is a worthwhile investment. They can diagnose the electrical connections definitively and test the catalytic converter's efficiency before you start throwing parts at it. You could end up saving money in the long run by avoiding unnecessary part replacements. The NOx sensor replacement might be necessary anyway, but it's best to be absolutely sure about the source.

Thanks a lot for the detailed explanation. I took it to a workshop, and you were right. There was a loose connection on the NOx sensor. They fixed the cable/plug connection for 95€ . Check engine light is off now and no more smell. Appreciate the advice!