Intake NOx Sensor
WARNING: This page is about a different car, the 2018 Nissan Titan XD. However, it is still accessible from the selected car via links, so may be relevant.
The intake NOx sensor is the first sensor mounted on the after treatment tubing, just in front of the DOC. This sensor measures the quantity of NOx in the exhaust gas before it enters the after treatment system. The intake NOx sensor includes a unique processor that is mounted externally from the sensor, and also includes a heater to bring the sensor to operating temperature quickly. The intake NOx sensor also detects the oxygen level in the exhaust.
The ECM compares the intake and outlet NOx sensor readings to determine the amount of NOx reduction that is achieved in the after treatment system, and to determine how much DEF to inject into the exhaust stream.