Diesel Exhaust Fluid Heater Control Unit

WARNING: This page is about a different car, the 2018 Land Rover Range Rover, 2017 Land Rover Range Rover, and 2016 Land Rover Range Rover. However, it is still accessible from the selected car via links, so may be relevant.

The Diesel Exhaust Fluid (DEF) heater control unit is located on the right side of the luggage compartment, behind the side trim panel. The heater system provides an adequate quantity of defrosted DEF that is available at all operating points. As a result, this enables rapid Selective Catalyst Reduction (SCR) system operation in the event of frozen DEF. The DEF heater control unit has a switched power supply from the Rear Junction Box (RJB), which is controlled by the Powertrain Control Module (PCM).

The DEF heater control unit has hardwired connections to the DEF tank module and the DEF line heater element. If the ambient air temperature is below -5°C (23°F), the PCM switches on the DEF heater control unit via the private Controller Area Network (CAN) bus. The DEF heater control unit energizes the heater elements, located in the DEF tank module and in the DEF line. The DEF heater control unit has on-board diagnostics to detect and report faults to the PCM via the private CAN bus.