If the fuel filler door does not open using the remote fuel filler door release button, you can open it manually. Pull the release located on the left side of the trunk compartment.
Hyundai Sonata LF 2014-2019 Owners Manual: Malfunction Indicator Lamp (MIL)
This warning light illuminates:
Once you set the ignition switch or Engine Start/Stop button to the ON position.
- It remains on until the engine is started.
When there is a malfunction with the emission control system. In this case,
have your vehicle inspected by an authorized HYUNDAI dealer ...
Hyundai Sonata LF 2014-2019 Service Manual: Components and Components Location
Component Location
1. Hood switch2. Burglar horn3. BCM4. Door lock / unlock buzzer5. Front door switch6. Rear door switch7. Trunk actuator & Switch
...