CITROËN C3 Handbook page 62

Access
If one of the doors or the boot is still
open or if the electronic key for the
Keyless Entry and Starting system has
been left inside the vehicle, the central
locking does not take place.
However, the alarm (if fitted) will be fully
activated after about 45 seconds.
If the vehicle is unlocked by mistake
and with no action on the doors or boot,
the vehicle will lock again automatically
after about 30 seconds.
If fitted to your vehicle, the alarm will
also be reactivated automatically.
60
As a safety measure (children on
board), never leave the vehicle without
taking the electronic key for the Keyless
Entry and Starting system with you,
even for a short period.
Be aware of the risk of theft when the
electronic key for the Keyless Entry and
Starting system is in one of the defined
zones with the vehicle unlocked.
In order to preserve the battery in the
electronic key and the vehicle's battery,
the "hands-free" functions are put into
long-term standby after 21 days without
use. To restore these functions, press
one of the remote control buttons or
start the engine with the electronic key
in the reader.
For more information on Starting with
Keyless Entry and Starting, refer to
the corresponding section.