NOx Sensor - Operation

OPERATION

There are two NOx modules and sensors used in the DEF fluid system, upstream and downstream. Both operate similarly to a wide band O2 sensor. The sensors are zirconium-based, multi-layer sensors with oxygen pumps. The NOx modules communicate the amount of NOx to the ECM over the J1939 communication bus. The upstream module is located on the right frame rail and the sensor is at the front of the Diesel Particulate Filter (DPF). The upstream module and sensor are used by the ECM to monitor NOx entering the catalyst. By comparing the inlet sensor to the outlet sensor, SCR efficiency can be determined by the ECM.