When the Smart Key fob is with you and you are within close proximity of the back of the vehicle, the hazard warning lights will blink and a chime will sound for about 3 seconds as an alert that the Smart Trunk is about to unlock.
Then the alert system will blink and chime two additional times before unlocking the Smart Trunk.
To enable the Smart Trunk, go to the Vehicle Settings in the Infotainment System. Press SETUP key/button, VEHICLE, DOOR, then enable SMART TRUNK.

During the Smart Trunk alert, the Smart Power Trunk can be deactivated with the Smart Key by pressing any button on the key fob.
For illustrative purposes only. Your actual display, buttons and/or features may vary.
Refer to section 4 in the Owner’s Manual for more information.