DTC P1691: Immobilizer-Antenna Coil Error: General Description
WARNING: This page is about a different car, the 2021 Kia Soul. However, it is still accessible from the selected car via links, so may be relevant.
Immobilizer (IMMO): A security device that permits vehicle to start only when the password code of key (transponder)/IMMO/EMS matches with each other to prevent vehicle theft.
When the wireless security authentication with the "IMMO ECU" and the "Key (TP)" is performed, the antenna disconnection connected to the "IMMO ECU" is judged.
The engine can not be started if antenna is disconnected.