If the Smart Key does not operate normally, you can lock or unlock the door by using the mechanical key.
Press and hold the release button (1) and remove the mechanical key (2). Insert the mechanical key into the key hole on the door.
To reinstall the mechanical key, put the key into the hole and push it until a click sound is heard.
Hyundai Sonata LF 2014-2019 Service Manual: Electric Parking Brake (EPB) Repair procedures
EPB Release
1.
Turn ignition switch OFF and disconnect the negative (-) battery cable.
2.
Connect the GDS to the data link connector located underneath the dash panel.
3.
Select and operate according to the instructions on the GDS screen.
(1)
Select vehicle name.
(2)
Select EPB.
...
Hyundai Sonata LF 2014-2019 Service Manual: Heater Core Repair procedures
Replacement
1.
Disconnect the negative (-) battery terminal.
2.
After loosening the bolts remove the main crash pad and cowl cross bar assembly together.
(Refer to Heater -"Heater Unit")
3.
Remove the heater core cover (A) after loosening the mounting screws.
4.
Pull out the heater ...