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 Powertrain Control Module (PCM) controls the heater supply voltage feed to the Diesel Exhaust Fluid (DEF) Dosing Control Unit via the SCR Relay 1. The DEF Tank electric heater and DEF Line Heater power supply and ground circuits are controlled by the DEF Dosing Control Unit. The DEF Tank Heater is integrated into the DEF Supply Pump Assembly and is not serviced separately.

Heating of DEF Supply Line and DEF Tank operate independent of each other. Line heating is based on the Ambient Temperature Sensor input and tank heating is based on the DEF Tank Temperature Sensor value. Heating of the line or tank heater is initiated when the corresponding temperature value is below -5°C (23°F). Heating is stopped when the corresponding temperature value goes above -4°C (24.8°F). The DEF Dosing Control Unit will illuminate the MIL light via the Powertrain Control Module (PCM) immediately after the diagnostics runs and fails. The DEF Dosing Control Module will turn off the MIL light via the PCM when the monitor runs and passes in three consecutive key cycles.