CITROEN DS3 Handbook page 40

Service indicator zero reset
After each service, the service indicator must
be reset to zero.
The procedure for resetting to zero is as
follows:
F switch off the ignition,
F press and hold the trip distance recorder
zero reset button,
F switch on the ignition; the distance recorder
display begins a countdown,
F when the display indicates "=0", release
the button; the spanner disappears.
Following this operation, if you wish to
disconnect the battery, lock the vehicle
and wait at least five minutes for the
zero reset to be taken into account.
Retrieving the service
information
You can access the service information at any
time.
F Press the trip distance recorder zero reset
button.
The service information is displayed for a
few seconds, then disappears.