See also:

Alarm and warning when the engine starts
When the Intelligent Key system warning light (  ) blinks red and the outside buzzer sounds, make sure the Intelligent Key is inside the vehicle. ...

Never leave these keys in the vehicle.
As many as 4 Intelligent Keys can be registered and used with one vehicle. The new keys must be registered by a NISSAN dealer prior to use with the Intelligent Key and NISSAN Vehicle Immobilizer ...

Troubleshooting guide
Verify the location of all Intelligent Keys that are programmed for the vehicle. If another Intelligent Key is in range or inside the vehicle, the vehicle system may respond differently than exp ...