2004 Trailblazer EXT trailering harness

I am new to the Trailblazer world, and am looking at towing our pop-up camper with this truck. The truck has the 7-pin wiring harness factory installed (as they all do, I believe). Does this include the brake control for the trailer, or would I need to install one of these?

:confused:

OK, I have read thru the manual, and know that I need ti install one. I found what I think is the pig tail to tie it into. (Looks like a blue wire, which would be for the brakes to the trailer, and a orange or red wire?)

I plugged the camper in, but I do not get any turn signals, headlights, or brake lights. I have verified that the camper lights are working properly by plugging the camper into another truck with factory wiring for the harness, and it works fine. I checked the fuses, and no problems there. Is there a switch or something that I need to connect to get the trailer harness to work?