CITROËN DS 4 Handbook page 292

Additive level
(diesel with particle filter)
According to your version of instrument panel,
the additive reservoir low level is indicated by:
- fixed illumination of the particle
filter warning lamp, accompanied
by an audible signal and a
message that the particle filter
additive level is too low,
or
- fixed illumination of the service
warning lamp, accompanied by
an audible signal and a message
that the particle filter additive
level is too low.
Topping up
The reservoir must be topped up without delay
by a CITROËN dealer or a qualified workshop.
Used products
Avoid prolonged contact of used oil or
fluids with the skin.
Most of these fluids are harmful to
health or indeed very corrosive.
Do not discard used oil or fluids into
sewers or onto the ground.
Take used oil to a CITROËN dealer or
a qualified workshop (France) or to an
authorised waste disposal site.