See Controls and Indicators → Instrument Lamps → Instrument Lamps. The illuminated key icon in the speedometer face indicates the status of the Harley-Davidson Smart Security System.

Armed: A key icon that blinks approximately every 3 seconds indicates that the system is armed.
Disarmed: After the ignition/headlamp switch is turned to IGNITION and the system disarms, the key icon will remain illuminated for approximately four seconds and then turn off.
Service: A key icon that remains illuminated longer than four seconds indicates that service of the module is required.