Theory of Operation
WARNING: This page is about a different car, the 2011 RAM Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.
The Diesel Exhaust Fluid system is used to reduce the amount of NOx being discharged through the exhaust system. The DEF Dosing Control Module receives feedback from the two NOx Sensors in the system. The first NOx Sensor is located before the SCR Catalyst, and the second NOx Sensor is located at the outlet of the SCR Catalyst. The DEF Dosing Control Module compares the two values to determine the conversion efficiency of the SCR Catalyst and the Diesel Exhaust Fluid system. The DEF Dosing Control Unit will illuminate the MIL light via the Powertrain Control Module (PCM) immediately after the diagnostics runs and fails.