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 Selective Catalytic Reduction (SCR) Catalyst is used in combination with the Diesel Exhaust Fluid system to reduce the amount of NOx gases produced during engine combustion. Excessive fuel or oil entering the exhaust system due to a failed engine component or Fuel Injector can cause the temperature to rise and will result in damage to the SCR Catalyst. The Powertrain Control Module (PCM) monitors the NOx concentration in the engine's exhaust gases using an aftertreatment Intake NOx Sensor and an aftertreatment Outlet NOx Sensor. By comparing these two values, the PCM is able to determine the conversion efficiency of the SCR catalyst and dosing system. The PCM illuminates the MIL immediately when the monitor runs and fails.