Theory Of Operation

WARNING: This page is about a different car, the 2013 RAM 3500 HD and 2013 RAM 2500 HD. However, it is still accessible from the selected car via links, so may be relevant.

The Diesel Exhaust Fluid (DEF) Supply Pump Assembly has many functions. It's primary purpose is to build adequate system pressure for dosing into the exhaust. When the system is shut down the pump is used to purge the fluid out of the line and back into the tank.The DEF Dosing Control Unit provides the 12 volt supply and ground for the pump. The DEF Dosing Control Unit also provides a Pulse Width Modulated (PWM) signal to the DEF Supply Pump Assembly to control the speed and output of the pump. The DEF Dosing Control Unit will illuminate the MIL light via the Powertrain Control Module (PCM) immediately after the diagnostics runs and fails and diesel exhaust fluid injection into the aftertreatment system is 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.