CITROEN C4 PICASSO Handbook page 206

Visibility
Rear wiper
If a significant accumulation of snow or
ice is present, deactivate the automatic
rear wiper via the "Driving assistance"
menu, then "Vehicle settings".
204
Rear wiper selection ring:
park,
intermittent wipe,
wash-wipe (set duration).
Reverse gear
When reverse gear is engaged, the rear wiper
will come into operation if the windscreen
wipers are operating.
This function can be deactivated in the
"Driving assistance" menu, then "Vehicle
settings".