Operating Door Locks from Outside the Vehicle
Mechanical key

If you lock the driver's door with a mechanical key, all vehicle doors will lock. If you unlock the driver's door with a mechanical key, the driver's door will unlock and the passenger doors will unlock according to the current two press unlock setting.
Once the doors are unlocked, they may be opened by pulling the door handle.
When closing the door, push the door by hand. Make sure that doors are closed securely.
Remote key

To lock the doors, press the Door Lock button (1) on the remote key. Press the Door Unlock button (2) on the remote key, the driver's door will unlock. If you press the Door Unlock button on the remote key again within four seconds, then all the doors will unlock.
Once the doors are unlocked, they may be opened by pulling the door handle.
When closing the door, push the door by hand. Make sure that doors are closed securely.
Information
Immobilizer System
Smart keyHyundai Elantra AD (2016-2020) Service Manual: Blind Spot Detection Unit Repair procedures
Removal
1.
Disconnect the negative (-) battery terminal.
2.
Remove the rear bumper.
(Refer to Body - "Rear Bumper")
3.
Remove the BSD unit (A) after loosening the mounting nuts.
•
Take care not to separate the bracket from rear bumper when removing the BSD se ...
Hyundai Elantra AD (2016-2020) Service Manual: Rear Door Trim Repair procedures
Replacement
•
Put on gloves to prevent hand injuries.
•
When removing with a flat-tip screwdriver or remover, wrap protective tape around the tools to prevent damage to components.
•
Be careful not to scratch the door trim and ot ...