Push Button Ignition Switch
WARNING: This page is about a different car, the 2017 Lincoln Navigator and 2017 Ford Expedition. However, it is still accessible from the selected car via links, so may be relevant.
The push button ignition switch is used to control the ignition mode.
There are 2 circuits the BCM and the RFA module monitor from the ignition switch to change the ignition mode. One circuit is monitored for voltage and the other for a ground signal. When the START/STOP button is pressed, one circuit routes battery voltage to the BCM, the PCM and the RFA module while a voltage signal from the BCM on the second circuit is routed to ground, indicating a request to change the ignition mode.
Changing the ignition mode from the OFF mode works in conjunction with the PATS. The modules must pass the PATS checks before the BCM changes the ignition mode out of OFF.