On the a large highway downhill above 73 mph, the ice turns on, but without throttle will it use fuel? I guess being fuel injected, it has to right?
Actually being fuel injected gives the ECU the flexibility to turn-off fuel altogether if no power is needed from the engine. It will be in "fuel cutoff". The engine will be dragged along by the car. Above a certain road speed the engine needs to run to avoid over speeding MG1. For Gen 2 Prius this was 42mph for Gen 4 it is over 60mph. kevin