Theory Of Operation

WARNING: This page is about a different car, the 2017 RAM 2500 HD. However, it is still accessible from the selected car via links, so may be relevant.

The Diesel Exhaust Fluid (DEF) Quality Sensor is mounted to the DEF tank and is used to detect the concentration of the DEF. The DEF Quality Sensor shares information with the Powertrain Control Module (PCM) over the J1939 Data Link. To determine the DEF concentration, the DEF Quality Sensor uses an internal temperature sensor to measure the temperature of the DEF. The DEF Quality Sensor monitors the internal temperature sensing element voltage and will fail this diagnostic if a short to ground/low voltage condition is detected within the sensor or the temperature sensing element reading is less than -40°C (-40°F) for 5 seconds. This diagnostic runs continuously with the key on, and the PCM will illuminate the MIL when the diagnostic runs and fails in two consecutive drive cycles. The PCM will turn off the MIL when the diagnostic runs and passes in three consecutive drive cycles.