Description - Diesel Exhaust Fluid Quality Sensor

The Diesel Exhaust Fluid (DEF) quality sensor is used to measure the quality of the DEF fluid. The sensor is based on ultrasonic technology that sends a very fast sound pulse through the fluid. The pulse reflects off the surface of the fluid and comes back to the sensor. Based on the time of flight and the strength of the pulse when it returns the sensor determines the concentration of DEF essentially based on density. The DEF quality sensor is a part of the DEF tank and is NOT  a serviceable component. If diagnosis leads to replacing the DEF quality sensor, then the entire DEF tank will need to be replaced as an assembly.