CITROEN DS3 Owner's Handbook Manual page 156

Deactivation
Only the passenger's front airbag can be
deactivated:
with the ignition off , insert the key in the
passenger airbag deactivation switch,
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 deployed.
Reactivation
When you remove a child seat that has
been fitted "rearwards facing", turn switch 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 in the
instrument panel, accompanied by
an audible warning and a message in
the multifunction screen, contact a CITROËN
dealer or qualified workshop to have the
system checked. The airbags may no longer be
deployed in the event of a serious impact.
If this warning lamp flashes, contact
a CITROËN dealer or a qualified
workshop. The passenger's front
airbag may no longer be deployed 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 it checked by a CITROËN dealer
or a qualified workshop.