CITROËN DS 5 Handbook page 104

Emergency starting with the
"Keyless Entry and Starting"
system
When the electronic key is in the recognition
zone and your vehicle does not start after
pressing the "START/STOP" button:
F Insert the electronic key in the reader.
F Press the brake pedal on vehicles with an
automatic gearbox, or fully declutch with a
manual gearbox.
F 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
recognition zone when driving or when you
(later) request switching off the engine, a
message appears in the instrument panel.
F 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.