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 the Diesel Exhaust Fluid (DEF) consumption by comparing the DEF pressure in the supply line to the known DEF Supply Pump volume. This rationality comparison will detect DEF consumption high or low failures. The PCM will illuminate the MIL light immediately after the diagnostics runs and fails. The DEF injection into the aftertreatment system will be disabled.