CITROËN DS 4 Handbook page 272

Before each use
Check that the towball is correctly fitted by verifying the following points:
- the towball is correctly locked in place (position A),
- the security key lock is on and the key removed; the locking wheel can no longer be
operated,
- the towball must no longer move at all in its carrier; try to shake it by hand.
during use
Never unlock the device when a trailer or load carrier is fitted to the towball.
Never exceed the maximum authorised weight for the vehicle plus trailer (Gross Train
Weight - GTW).
Before driving, check the adjustment of the headlamp beam height.
For more information on adjusting the headlamps, refer to the corresponding section.
After use
For journeys made without a trailer or load carrier, the trailer harness socket must be folded
away, the towball removed and the blanking plug inserted in the carrier. This measure
applies particularly if the towball could hinder visibility of the number plate or lighting.
Fitting the towball
Remove the protective plug from the carrier
and check the condition of the fixing system.
If necessary, clean the carrier with a brush or
clean cloth.
Take the towball from the storage bag.
Remove the protective cover from the ball and
the protective cap from the locking wheel.
Stow the plug, cover and cap in the storage
bag.
Check that the towball is unlocked (position B).
If not, insert the key in the lock and turn the key
anti-clockwise to unlock the mechanism.