DTC Description
WARNING: This page is about a different car, the 2021 Hyundai Kona. However, it is still accessible from the selected car via links, so may be relevant.
The FCA (Forward Collision-Avoidance Assist) module sets C1620-78 when it detects an FCA Sensor Alignment Error.
Sensor Alignment can be only conducted when the vertical, horizontal angle of the sensor are within the normal range. Thus, check for sensor bracket, vehicle deformation, and so forth before Alignment.