Trailer wiring harness

Hello - I have a 94 GMC Jimmy, I need help with installing a T-style trailer hitch wiring harness, but am unable to find the harness under the car.

I took one of the rear tail-lights off and found all the wiring coming thru a grommet from the body of the car.

Any help would be greatly appreciated.

BTW - this car already has a factory installed class I trailer hitch attached below the bumper by the license plate area.

Thanks

I was thinking some of these vehicles had wires for a trailer wiring plug taped to a harness near the rear bumper

A '94 might be the same as a '93 in that the harness is in the jack storage and needs to be fished out.

For my 94 I took the rubber trim piece off the floor by the tail gate and all the wires were there to access. Then I ran the jumpers(trailer) wires back to the jack compartment and stored them in there.

Thanks for all the replies, will look at the areas mentioned and let you know what I find.