Below a specified temperature the PCM commands the Glow Plug Control Module (GPCM) to activate
the heaters in the reductant system.
The reductant system has heaters in the tank, pump, and lines. The heaters in the tank thaw the DEF if it is frozen
and allow it to flow to the pump without freezing. The heaters in the pump and lines allow the DEF to flow to the
injector without freezing.