Whether the wiring is there depends on what vehicle you have.
I looked for that info by scrolling back to the last 5 posts you made in this thread and couldn't find anyplace where you identified your vehicle, other than a Jeep, I assume with the Wilderness package.
If your vehicle did not come with a rear sub initially, then it will not have the wiring for it. It also will not have 3 out the 4 mounting cleats for the rear sub, if you have a Suburban. I don't know how the Tahoe/Yukon shore wheel bases models mount, other than they are different from the Suburbans / YukonXLs.