Theory Of Operation
WARNING: This page is about a different car, the 2014 RAM 1500. However, it is still accessible from the selected car via links, so may be relevant.
The Powertrain Control Module (PCM) monitors Diesel Exhaust Fluid (DEF) pressure and DEF Supply Pump lifts to determine frost build-up in the DEF Inlet and DEF Outlet lines. If the DEF Supply Pump lifts are too frequent and one of the DEF line pressure inputs is outside a calibrated threshold, the PCM will turn on the Malfunction Illumination Lamp (MIL) and set the DTC.