With the door lock button

Information
If a power door lock ever fails to function while you are in the vehicle try one or more of the following techniques to exit:
With the central door lock switch

When pressing the (
) switch (1),
all vehicle doors will lock.
When pressing the (
) switch (2),
all vehicle doors will unlock.
If the key is in the ignition switch and any door is opened, the doors will not lock even though the lock button (1) of the central door lock switch is pressed.
If the smart key is in the vehicle and any door is opened, the doors will not lock even though the lock button (1) of the central door lock switch is pressed.
WARNING
WARNING
Do not leave children or animals unattended in your vehicle. An enclosed vehicle can become extremely hot, causing death or serious injury to unattended children or animals who cannot escape the vehicle. Children might operate features of the vehicle that could injure them, or they could encounter other harm, possibly from someone gaining entry to the vehicle.
WARNING
Always secure your vehicle.
Leaving your vehicle unlocked increases the potential risk to you or others from someone hiding in your vehicle.
To secure your vehicle, while depressing the brake, move the shift lever to the P (Park) position, engage the parking brake, and place the ignition switch in the LOCK/OFF position, close all windows, lock all doors, and always take the key with you.
WARNING
If you stay in the vehicle for a long time while the weather is very hot or cold, there are risks of injuries or danger to life. Do not lock the vehicle from the outside when someone is in the vehicle.
CAUTION
Opening a door when something is approaching may cause damage or injury. Be careful when opening doors and watch for vehicles, motorcycles, bicycles or pedestrians approaching the vehicle in the path of the door.
Smart key
Auto Door Lock/ Unlock FeaturesHyundai Elantra AD (2016-2020) Service Manual: Delivery Pipe Repair procedures
Removal
1.
Turn the ignition switch OFF and disconnect the battery negative (-) cable.
2.
Release the residual pressure in fuel line.
(Refer to Fuel Delivery System - "Release Residual Pressure in Fuel Line")
•
When removing the fuel pump relay, a Diagnostic Tr ...
Hyundai Elantra AD (2016-2020) Service Manual: ETC (Electronic Throttle Control) System Troubleshooting
Fail-Safe Mode
ItemFail-SafeETC MotorThrottle valve stuck at 7°TPSTPS 1 faultReplace it with TPS 2TPS 2 faultReplace it with TPS 1TPS 1,2 faultThrottle valve stuck at 7°APSAPS 1 faultReplace it with APS 2APS 2 faultReplace it with APS 1APS 1,2 faultEngine idle state
...