That is one nasty looking 7-way plug/connector. Looks like it has been sitting in water for months along with road salt.

Lemme go see what google has to say.
Okay, back...
Did you know that they actually make a brush specifically to clean these connectors? (I know I didn't.) Available at your local auto parts store (Napa is $30):

Or for something fancier and around $70 + shipping you could get one of these. Great way to impress friends. :) Hmmm, wonder if this would also work in a CG pedestal recept.?? :B

'Course, you could just go buy a replacement connector for like $6 (ebay) instead of cleaning it.