DTC B1603-00: CAN Bus OFF: 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.
The IBU-SMK is one of modules that make up the body control system. The IBU-SMK uses B-CAN to communicate with other modules to receive required data and transmit needed data.