CITROËN DS 4 Handbook page 294

Particle filter (diesel)
According to your version of instrument panel, the start of
saturation of the particle emissions filter is indicated by:
- fixed illumination of the particle
filter warning lamp, accompanied
by an audible signal and a
message that there is a risk of
blockage of the particle filter,
or
- temporary illumination of
the service warning lamp,
accompanied by an audible
signal and a message that
there is a risk of blockage of
the particle filter.
As soon as the traffic conditions permit,
regenerate the filter by driving at a speed of at
least 40 mph (60 km/h) until the warning lamp
goes off.
If the warning lamp stays on, refer to the
"Additive level" section.
On a new vehicle, the first operations
of regeneration of the particle filter
may be accompanied by the smell of
"burning", which is perfectly normal.
Following prolonged operation of the
vehicle at very low speed or at idle,
you may, in exceptional circumstances,
notice the emission of water vapour at
the exhaust on acceleration. This does
not affect the behaviour of the vehicle
or the environment.
Manual gearbox
The gearbox does not require any
maintenance (no oil change).
Refer to the manufacturer's service
schedule for the checking interval for
this component.
Automatic gearbox
The gearbox does not require any
maintenance (no oil change).
Refer to the manufacturer's service
schedule for details of the level
checking interval for this component.