DTC Description: Notes
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 engine control module (ECM) monitors the NOx concentration in the engine's exhaust gases using an after treatment intake NOx sensor and an after treatment outlet NOx sensor. By comparing these two values, the ECM is able to determine the conversion efficiency of the SCR catalyst and dosing system. This diagnostic uses SCR conversion efficiency from the NOx sensors to determine when the DEF tank has been filled with poor quality DEF in conditions where the fluid level in the tank is too low for the Urea Quality Sensor to read the DEF concentration.