What Is A NOx Sensor?

The NOx sensor is a device/component which measures the levels of nitrogen emitted from your vehicle.

NOx sensors are just one of the components that comprise the NOx reduction after-treatment system, which is responsible for reducing harmful exhaust gases and protecting the environment in diesel vehicles with urea-based SCR systems.

Depending on the vehicle’s make and model, the components present can vary. A typical system would comprise a turbocharger, a DPF, and an SCR catalyst – with the NOx sensor sitting upstream from the catalyst.

More than one NOx sensor may be present in some vehicles, featuring both an upstream and downstream sensor.

With this assembly, the first sensor is installed near the turbo downpipe, which measures the engine-output NOx, with the second sensor measuring the NOx levels exiting the SCR catalyst.