NOx sensor

NOx sensors are distinguished by the highest level of precision and reliability in the regeneration of the NOx storage catalytic converter.
NOx sensor from NTK

To make petrol engines more environmentally friendly, manufacturers are focussing on direct injection petrol engines that can be operated within the lean range when run at partial load. That entails 12 to 20 per cent less consumption - however it also requires a special NOx storage catalytic converter and an NOx sensor. NOx sensors are distinguished by the highest level of precision and reliability in the regeneration of the NOx storage catalytic converter.

Method of operation of the NOx sensor

In lean, stratified charge operation the operating point of the engine no longer lies at lambda = 1 and therefore lies outside the optimal conversion window for the catalytic converter. Nitrogen oxides can no longer be optimally converted by it and thus increase considerably. For this reason an additional NOx storage catalytic converter is used, which temporarily stores the nitrogen oxides.

Functional principle of the NOx lambda sensor

If its storage capability is depleted, the NOx sensor recognises it. It signals to the engine control that the system must be switched over for about two seconds to rich operation (λ<1). The nitrogen oxides are reduced and converted into harmless nitrogen. This "regeneration phase" repeats about every 60 seconds in lean operation.

Cable assignment

NTK NOx lambda sensors have six cable connections. The heating element is supplied with voltage through yellow and blue. The signal of the pump current flows through the white cable (Ip I (+)) and the green (IP II (+)) cable; the signal of the measurement cell (Vs+) flows through the grey cable. The black cable represents the earth connection for pump and measurement cells.

Cable assignment of the NOx lambda sensor