Hyundai Sonata Hybrid 2017 Owner's Manual page 323

Driving your vehicle
Button Position
ON
Press the Engine Start/Stop button while it
is in the ACC position without depressing
the brake pedal.
The warning lights can be checked before
the hybrid system is started.
START
To start the hybrid system, depress the
brake pedal and press the Engine
Start/Stop button with the shift lever in the P
(Park) position.
5-8
Action Notice
Do not leave the Engine Start/Stop button in
the ON position when the hybrid system is
not running to prevent the battery from dis-
charging.
If you press the Engine Start/Stop button
without depressing the brake pedal, the
hybrid system does not start and the Engine
Start/Stop button changes as follows:
OFF → → ACC → → ON → → OFF or ACC