Ignition Switch System: Off
WARNING: This page is about a different car, the 2020 Ford F-150. However, it is still accessible from the selected car via links, so may be relevant.
The BCM supplies voltage to the ignition switch at all times. When the ignition switch is in the OFF position, the switch is open, preventing any voltage signals from reaching the BCM. When the BCM does not detect voltage from any of the ignition mode-designated circuits, the BCM interprets this as the ignition off mode.
The BCM communicates the ignition mode to the other modules by sending an ignition status message over the CAN and does not energize any relays to prevent voltage from being distributed to the various electrical systems.