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 (DEF) Supply Pump Assembly has an internal heater to prevent the fluid from freezing inside the pump. The power supply and control circuits are controlled by the DEF Dosing Control Unit. The DEF Supply Pump Heater is integrated into the DEF Supply Pump Assembly and is not serviced separately. The DEF Dosing Control Unit will illuminate the MIL light via the Powertrain Control Module (PCM) immediately after the diagnostics runs and fails and the line heater will be disabled. The DEF Dosing Control Unit will turn off the MIL light via the PCM when the monitor runs and passes in three consecutive key cycles.