This indicator light illuminates:
Hyundai Sonata LF 2014-2019 Service Manual: Outside Rear View Mirror Components and Components Location
Component Location
1. Outside rear view mirror
...
Hyundai Sonata LF 2014-2019 Service Manual: Muffler Components and Components Location
Components
1. Front muffler2. Center muffler3. Main muffler4. Gas ket5. Hanger
...