CITROEN C4 Spacetourer Handbook page 158

Driving
When the adaptive cruise control is
automatically paused, it can only be
reactivated when safe conditions are
restored. The message "Activation
not possible, conditions unsuitable"
is displayed while reactivation is not
possible.
When the conditions allow, it is
recommended that the function be
reactivated by pressing button 2 or 3,
which will make the current speed of your
vehicle the new cruise speed setting,
rather than by pressing button 4 (on/
pause) which reactivates the cruise control
using the old cruise speed setting, which
may be very different from the current
speed of your vehicle.
Operating limits
The adaptive cruise control uses only engine
braking to slow the vehicle. Consequently the
vehicle loses speed slowly, as when releasing
the accelerator pedal.
The system is paused automatically:
- if the vehicle in front slows down too much
or too suddenly, and the driver does not
brake,
- if a vehicle comes between your vehicle and
the vehicle in front.
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- if the system does not slow the vehicle
enough to continue to maintain a safe
distance, for example when descending
a steep hill.
The regulation range is limited to a maximum
difference of 19 mph (30 km/h) between the
cruise speed setting and the speed of the
vehicle in front. Above this, the system goes into
pause if the safety distance becomes too short.
Poor weather conditions (very heavy
rain, accumulation of snow in front of the
radar) may hinder the operation of the
system, with the display of the operating
fault message "SYSTEM INACTIVE:
Reduced visibility". The function remains
unavailable until the message disappears.
Since the radar detection range is relatively
narrow, it is possible that the system cannot
detect:
- vehicles of reduced width, such as
motorcycles, for example,
- vehicles not running in the middle of the
lane,
- vehicles entering a corner,
- vehicles changing lane at the last moment.
The cruise control does not take account of:
- stationary vehicles,
- vehicles driving in the opposite direction.
Malfunction
In the event of a malfunction of the adaptive
cruise control system, you are warned by an
audible signal and the display of the message
"Driving aid functions fault".
Have the system checked by a CITROËN
dealer or a qualified workshop.