What is an NOx sensor?
NOx is an abbreviation for nitrogen oxide: English for nitrogen oxide. In fact, an NOx sensor is a 2nd lambda sensor that is mounted behind the catalytic converter in the exhaust. We still know the original lambda sensor from the time when cars had no catalytic converter. But where the lambda sensor had to measure the oxygen content, the NOx sensor registers the amount of nitrogen after the exhaust gases have first been in the catalytic converter. In this way, the functionality of the catalytic converter is tested and its values are sent to the engine management system.