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.

When the DEF Dosing Control Unit is in pressure control mode, it provides a Pulse Width Modulated (PWM) signal to turn on the DEF Supply Pump Assembly to refill the lines. As the lines fill, the pressure builds to the set point. When the pressure reaches the set point, the DEF Dosing Control Unit turns on the DEF Injector to bleed air out of the Pressure Line. Each time the injector is turned off, the DEF Dosing Control Unit the amount of time it takes for the pressure to rise back to the set point to determine when all of the air is bled out of the line. The DEF Dosing Control Unit will illuminate the MIL light via the 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.