The audio system is disabled when it is disconnected from the power source, such as when the battery is disconnected or goes dead. In certain conditions, the system may display a code entry screen. If this occurs, reactivate the audio system.
Reactivating the audio system
1. Turn the ignition switch to ON *1.
2. Turn on the audio system.
3. Press and hold the audio system power button for more than two seconds.
The audio system is reactivated when the audio control unit establishes a connection with the vehicle control unit. If the control unit fails to recognize the audio unit, you must go to a dealer and have the audio unit checked.
Honda Civic Owners Manual. HFL Buttons
(Pick-up) button: Press to go
directly to the Phone screen or to answer an
incoming call.
(Hang-up/back) button: Press to end
a call or to cancel a command.
(Talk) button: Press to call a
number with a stored voice tag.
(Phone) button: Press to go
directly to the Phone screen. ...