CITROEN DS5 Owner's Handbook Manual page 104

Emergency starting with the
Keyless Entry and Starting
system
When the electronic key is in the defined zone
and your vehicle does not start after pressing
the "START/STOP" button:
Insert the electronic key in the reader.
Press the brake pedal on vehicles with
automatic gearbox or electronic gearbox
system, or fully declutch with a manual
gearbox.
Press the "START/STOP" button.
The engine starts.
Emergency switch-off
In the event of an emergency only, the engine
can be switched of without conditions. To do
this, press and hold the "START/STOP" button
for about 3 seconds.
In this case the steering column locks as soon
as the vehicle stops.
Electronic key not recognised by
the "Keyless Entry and Starting"
system
If the electronic key is no longer in the defined
zone when driving or when you (later) request
switching off the engine, a message appears in
the instrument panel.
Press and hold the "START/STOP"
button for about 3 seconds if you want to
force switching off the engine (note that
restarting will not be possible without
the key).