CITROEN C4 PICASSO Handbook page 216

Safety
Under-inflation alert
This is given by fixed illumination of
this warning lamp, accompanied by
an audible signal and, depending on
equipment, the display of a message.
F Reduce speed immediately, avoid
excessive steering movements and sudden
braking.
F Stop the vehicle as soon as it is safe
to do so.
The loss of pressure detected does not
always cause visible bulging of the tyre.
Do not satisfy yourself with just a visual
check.
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F In the event of a puncture, use the
temporary puncture repair kit or the spare
wheel (depending on equipment),
or
F if you have a compressor, such as the one
in the temporary puncture repair kit, check
the pressures of the four tyres when cold,
or
F if it is not possible to make this check
immediately, drive carefully at reduced
speed.
The alert is maintained until the system
is reinitialised.
Reinitialisation
It is necessary to reinitialise the system every
time one or more tyre pressure is adjusted, and
after changing one or more wheels.
A label attached to the middle pillar, driver's
side, gives a reminder of this.