Following my fuse-box thread I'm getting closer for installing.

I have a question about dosing pump wiring. What i've got:


I know missing frame and extraction unit. Anyways i have question about wiring.
I know GND goes to earth point 682, that is behind C-pillar cover, but where does the rubber plug, that is seen in the picture, go?
Surfing the web and ETKA, doesn't give me the answer.

Thanks.