If the LED lamp does not operate, have the vehicle checked by an authorized HYUNDAI dealer.
Hyundai Sonata LF 2014-2019 Service Manual: Repair procedures
Compession Pressure Inspection
If the there is lack of power, excessive oil consumption or poor fuel economy, measure the compression pressure.
1.
Make sure the oil in the crankcase is of the correct
viscosity and at the correct level and that the battery is correctly ...
Hyundai Sonata LF 2014-2019 Service Manual: Thermostat Components and Components Location
Components
1. Water inlet fitting2. Thermostat
...