it's at the rear behind the left side cover. once the cover is pull you should see a plug in.
You may have to go to the dealer to get the proper wiring harness.
2006 Dodge Dakota - Where do i find the trailer wiring harness
You can find a trailer wiring harness for a Chevrolet in a Haynes repair manual. The manuals are available at most auto parts stores.
Trailer wiring harness part #118382 - any local Auto Parts Store should care this.
Get a wiring kit that has the in-line connectors that plugs into your existing wiring harness. The kits come with instructions with the location of the connector for your van. Here is one example; http://www2.northerntool.com/product/200325022.htm
under the car,behind spare tire,is the wiring harness with access plug for dodge trailer harness (optional) my came with 2012 journey
The factory wiring harness for the trailers will plug in under the back of the vehicle in the area of the spare tire, the harness plugs into the wiring harness for the tail lights.
when you buy the harness to wire in, the intructions for correct wiring will be on the harness packaging
Subarus all have a connector for a trailer wiring harness built in. There is a supplemental trailer harness that you purchase from your hitch supplier and it just plugs right in. Instructions are available on-line. This one is for a 2001, but they have been the same for a number of years.
http://www.installdr.com/QuickWiring.html
You can find a wiring diagram that shows you how to hook up a trailer wiring harness on a 1998 Pontiac Transport at most auto parts stores. A Pontiac repair manual should have the diagram in it.
you do not need the extra 7 pin if your not running electri brakes
Not all trucks are built with a trailer harness plug. If you can not find one, then your truck does not have one and you need to install one.