Zan,
These sensors are known to fail. Make sure you test power between the red and black wire at the connector, battery voltage. Using the black wire as negative, check the green and yellow wire for about 2 to 2.5 volts. If voltage checks are good, replace sensor. Good Luck
Thanks. Yep. We're dropping the tank to get to the sensor. Going to try cleaning it.
DEF quality sensor error check the power and negative to the def tank header and the canbus also there is 10a fuse for the voltage input