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 Diesel Exhaust Fluid (DEF) Injector is mounted to the decomposition tube at the inlet of the Selective Catalytic Reduction (SCR) Catalyst. The Powertrain Control Module (PCM) sends a Pulse Width Modulated (PWM) signal to DEF Injector to vary the amount of fluid sprayed into the exhaust stream. The PCM will illuminate the MIL lamp after this diagnostic runs and fails. This is a two Trip Fault.