CITROEN DS4 Owner's Handbook Manual page 180

Deactivation
In exceptional conditions (starting a vehicle
which is bogged down, stuck in snow, on soft
ground...), if you are unable to make progress,
it may be advisable to temporarily deactivate
these systems, so that the wheels can spin
freely and allow the vehicle to move.
Press the "ESP OFF" button,
located near the steering wheel.
If this warning lamp comes on in the instrument
panel and the indicator lamp in the button
comes on, this indicates that these systems are
deactivated.
It is recommended that the systems be
reactivated as soon as possible.
Reactivation
These systems are reactivated automatically
each time the ignition is switched back on or
from 30 mph (50 km/h).
Press the "ESP OFF" button again to
reactivate them manually.
Operating fault
If this warning lamp comes on,
accompanied by an audible signal
and a message in the screen, this
indicates a fault with these systems.
Have it checked by a CITROËN dealer or a
qualified workshop.
The trajectory control systems offer
increased safety in normal driving, but
this should not encourage the driver to
take extra risks or drive at high speed.
The correct functioning of these
systems is assured provided that
manufacturer's recommendations are
observed on:
- wheels (tyres and rims),
- braking components,
- electronic components,
- assembly and repair procedures.
After an impact, have these systems
checked by a CITROËN dealer or a
qualified workshop.