When Monitored
WARNING: This page is about a different car, the 2015 RAM 3500 HD and 2015 RAM 2500 HD. However, it is still accessible from the selected car via links, so may be relevant.
Engine Running. When the Exhaust Gas Temperature (EGT) 3 Sensor, Diesel Exhaust Fluid (DEF) Tank Temperature, and the Ambient Temperature Sensor all reach a calibrated threshold in a pre-determined amount of time. The Powertrain Control Module (PCM) then begins to monitor the DEF system as it attempts to prime the DEF Pump.