CITROËN DS 4 Handbook page 212

deactivation
At any time, press the "ECO OFF" switch to
deactivate the system.
This is confirmed by the switch warning lamp
coming on accompanied by the display of a
message.
If the system has been deactivated
in STOP mode, the engine restarts
immediately.
Reactivation
Press the "ECO OFF" switch again.
The system is active again; this is confirmed
by the switch warning lamp going off and the
display of a message.
The system is reactivated automatically
at every new start using the key or the
"START/STOP" button.