DTC B2191, P1615: Difference Of Key: Description
WARNING: This page is about a different car, the 2012 Nissan Altima. However, it is still accessible from the selected car via links, so may be relevant.
Performs ID verification through BCM and Intelligent Key when push-button ignition switch is pressed. Prohibits starting of the engine when an unregistered ID of Intelligent Key is used.