This indicator light illuminates
When there is a malfunction on the low washer, Smart cruise control, and so on.
To identify the details of the warning, look at the LCD display.
Hyundai Sonata LF 2014-2019 Service Manual: Sunvisor Components and Components Location
Component Location
1. Sunvisor2. Retainer
...
Hyundai Sonata LF 2014-2019 Owners Manual: Warning messages
WARNING
Whenever leaving the vehicle or parking, always come to a complete stop
and continue to depress the brake pedal. Move the shift lever into the P (Park)
position, press the EPB switch, and press the Engine Start/Stop button to the
OFF position. Take the Smart Key with you when exiting ...