DEF Line Heater
WARNING: This page is about a different car, the 2018 Nissan Titan XD. However, it is still accessible from the selected car via links, so may be relevant.
A DEF line heater is located at the end of the DEF dosing line where it meets the DEF pump. This heater is used to heat the dosing line between the DEF pump and the DEF dosing valve to prevent freezing during vehicle operation.