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) Tank has an internal heating coil to help eliminate freezing of Diesel Exhaust Fluid. The DEF Dosing Control Unit monitors the temperature of the Diesel Exhaust Fluid inside the tank. When it is determined that the Diesel Exhaust Fluid needs to be heated, the DEF Dosing Control Unit opens the DEF Engine Coolant Valve which is located nest to the DEF Tank, and allows warm engine coolant to circulate through the heating coil inside the tank to warm the Diesel Exhaust Fluid in the tank. The DEF Dosing Control Unit will illuminate the MIL lamp via the Powertrain Control Module (PCM) immediately after this diagnostic runs and fails. The DEF Dosing Control Unit will turn off the MIL lamp via the PCM immediately after the diagnostic runs and passes for three consecutive key cycles.