Greetings,

We installed a trailer harness on my wife's '03 Sorento, albeit not a Uhaul
brand.  We were able to tap into the existing connector under the right rear
quarter panel (accessible from underneath) where the Kia brand harness plugs
in.  I just cut off the Kia harness plug and spliced the wires directly to
the ends of the new harness.  We also had to use a power module because the
power from the existing harness wasn't enough for our trailer lights (per
the book).  It was no big deal and you can hear the module click when the
turn signals flash even if we don't have a trailer attached.

I can't remember if we had a diagram of which wire controlled which light on
the Sorento's harness or if I used a test light (it was over three years
ago), but at least having the factory plug right there meant I didn't have
to splice into each individual wire for each light.  There's also a little
hidden space where the power module can hide and not get dirty.

Cheers - Jonathan