The answer is simple. : Thumbup:
The hybrid system does not have the engine, unless you have at least 7.5 L of fuel in the tank.
See page 94 in the english manual: -
■ Running out of fuel
When the vehicle has run out of fuel and the system can not be started,
Refuel the vehicle with at least enough gasoline to the low fuel level
Warning light (P 598). If there is only a small amount of fuel, the
Hybrid system may not be able to start. (The standard amount of fuel is about
7.5 L [2.0 gal., 1.7 Imp.gal.], When the vehicle is on a level surface. This value
May vary when the vehicle is on a slope. Add extra fuel when the vehicle is
inclined.)
RTFM (Read The F ***** g Manual ...): Evil: