Ducati MULTISTRADA 1200S ABS 2015 Workshop Manual page 665

Screw the lower part (13) of the plug fully on its upper part (14) while holding with tool no. 88713.4303 the
upper part.
Screw ring nut (12) to the plug bottom part (13), bringing the ring nut fully home on the upper part (14).
Hold with tool no. 88713.4303 the plug upper part during the operation.