Theory Of Operation

The Diesel Exhaust Fluid (DEF) Quality Sensor is welded 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 designated Data Link circuits. To determine the DEF concentration, the DEF Quality Sensor transmits an ultrasonic signal to measure the density of the DEF. It also an internal temperature sensor to measure the temperature of the DEF. This diagnostic runs continuously with the key on, and the PCM will illuminate the MIL after the diagnostic runs and fails during a drive cycle. The PCM will turn off the MIL after the diagnostic runs and passes in three consecutive drive cycles.