Theory Of Operation

The Diesel Exhaust Fluid (DEF) Tank has an internal heating coil to help eliminate freezing of Diesel Exhaust Fluid. The DEF Dosing Control Unit monitors the temperature of the Diesel Exhaust Fluid inside the tank. When it is determined that the Diesel Exhaust Fluid needs to be heated, the DEF Dosing Control Unit supplies power and ground to the electronic DEF Tank Heater to warm the Diesel Exhaust Fluid in the tank. The DEF Tank Heater is integrated into the DEF Pump assembly and is not serviced separately. The Powertrain Control Module (PCM) will illuminate the MIL lamp after the diagnostic runs and fails in two consecutive drive cycles. The DEF Dosing Control Unit will turn off the MIL lamp via the PCM immediately after the diagnostic runs and passes for three consecutive key cycles.