System Operation - Push Button Ignition Switch: Acc

WARNING: This page is about a different car, the 2016 Ford Expedition. However, it is still accessible from the selected car via links, so may be relevant.

When the START/STOP button is momentarily pressed and released when the ignition is off and the brake pedal is not applied, the RFA module checks the vehicle for a valid programmed key as part of the PATS function. If it detects a valid programmed key, the RFA module sends a message to the BCM indicating a valid programmed key is detected. The BCM then provides power to the systems designed to operate when the ignition is in the ACC mode.

When the BCM changes the ignition mode, it communicates the ignition mode to the other modules by sending an ignition status message over the CAN.

The RFA module must recognize a valid programmed key before the BCM changes the ignition mode out of OFF. If no valid programmed key is detected, the ignition remains off.