Key ON Engine OFF (KOEO) Self-Test
WARNING: This page is about a different car, the 2020 Ford F-550 Super Duty, 2020 Ford F-450 Super Duty, 2020 Ford F-350 Super Duty, 2020 Ford F-250 Super Duty, and 2020 Ford F-150. However, it is still accessible from the selected car via links, so may be relevant.
The KOEO self-test is a functional test of the PCM carried out with the ignition ON and the engine OFF. This test checks that all inputs and outputs (circuits, sensors, regulators, relays, and solenoids) connected to the PCM are electrically operating without a concern.