CITROEN DS3 Owner's Handbook Manual page 122

Deactivation
Only the passenger's front airbag can be
deactivated:
with the ignition off, insert the key in the f
passenger airbag deactivation switch 1 ,
turn it to the "OFF" position,
then, remove the key keeping the switch in
the new position.
This warning lamp comes on in the
instrument panel when the ignition is
on and until the airbag is re-activated.
To assure the safety of your child,
the passenger's front airbag must
be deactivated when you install a
"rear facing" child seat on the front
passenger seat.
Otherwise, the child would risk being
seriously injured or killed if the airbag
were triggered.
Reactivation
When you remove the child seat, turn switch 1 to
the "ON" position to re-activate the airbag and
so assure the safety of your front passenger in
the event of an impact.
With the ignition on, this warning
lamp comes on in the instrument
panel for approximately one minute,
if the passenger's front airbag is
activated.
Operating fault
If this warning lamp comes on on the
instrument panel, accompanied by an
audible warning and a message on
the multifunction screen, contact a CITROËN
dealer to have the system checked. The
airbags may no longer be triggered in the event
of a serious impact.
If this warning lamp flashes, contact
a CITROËN dealer. The passenger's
front airbag may no longer be
triggered in the event of a serious
impact.
If at least one of the two airbag
warning lamps come on continuously,
do not install a child seat on the front
passenger seat.
Have the system checked by a
CITROËN dealer.