Removes and Installs the Water Sensor Located on the Fuel Filter on 2012 – 2016 6.6L Duramax Diesel Engines. The 42mm wrench also works on 2013 and newer 6.7L Cummins. For use when replacing the fuel filter or when servicing the water sensor. The plastic sensor has a new hex design that is easily damaged by tools, like pliers, that do not specifically fit the sensor.