Anti-Theft Alarm System (for some vehicle versions)
The anti-theft alarm helps prevent theft of the vehicle or of valuables from the passenger compartment and cargo area. If an unauthorized attempt is made to enter the vehicle or remove the audio system, the horn sounds and the turn signal indicators begin to flash.
The audible alarm operates for 30 seconds, after which the anti-theft system returns to standby mode.
To return the anti-theft system to standby mode without waiting for the 30 seconds to elapse, unlock the driver's door with the key or the remote keyless entry transmitter.

On vehicles with ultrasonic sensors, the anti-theft system can only be disarmed using the remote control transmitter.
If the driver's door lock is unlocked with the key, the alarm will sound because the anti-theft system is not disarmed.
The security alarm automatically switches to standby mode 15 seconds after all passenger doors, the tailgate/liftgate and the hood are closed (if the vehicle is equipped with ultrasonic sensors, the security alarm is set to standby mode after 25 seconds).
To activate the security alarm system, lock the door locks from outside the vehicle using the key or the remote keyless entry transmitter. The activation of the security alarm is indicated by the blinking of the indicator light located on the instrument panel.
To activate the ultrasonic sensors at the same time as the security system is set to standby mode, lock all doors, including the tailgate/liftgate, using the key or the remote keyless entry transmitter.
When locking the doors with the key or the remote keyless entry transmitter, all turn signal lamps and the turn signal indicators on the instrument panel flash three times to confirm that the locks are engaged and the security system is activated. When unlocking the doors, these devices flash once.
The security system is also set to standby mode when the doors, including the tailgate/liftgate, are locked using the driver's door lock knob or the central locking master switch (while simultaneously pressing the outside door handle).
After the security alarm system has been set to standby mode, opening any vehicle door (without using the key or the remote keyless entry transmitter), the tailgate/liftgate or the hood will trigger the alarm.
The audible alarm also activates if the audio unit is removed from its slot in the instrument panel or if its wiring harness is cut.
In addition, the security alarm is triggered if a passenger remaining in the locked vehicle attempts to turn the ignition switch on.
Vehicles equipped with the Double Locking (Superlock) system: If you have activated both the double locking system and the security alarm, the security alarm will not be triggered if a passenger attempts to open the door from the inside using the door lock knob or the central locking master switch.
The security alarm will not be set to standby mode if the tailgate/liftgate, the hood or any vehicle door is not fully closed. If the security alarm does not activate, check the open door warning messages displayed on the multi-information display (see page 99). Since information about a hood that is not fully closed is not displayed, check the hood manually.
Do not attempt to make any changes or additions to this system or to related devices.
Test yourself
A quick Honda Civic quiz: every answer comes with an explanation and a link to the manual page.