Trailer wiring harness in a 2003

HI,

I am trying to wire/ install a converter for a trailer. The handbook says there is a trailer wiring harness. The dealer says it is in the rear right corner but can't say where, for sure, without looking. I have looked in the jack storage compartment and there are wires and a black box there but nothing that appears dedicated (like a pigtail). The hitch installer says it is under the car on the drivers side. Do I just need to look harder or perhaps some place else?

Thanks,

On mine, its under the plastic housing where the compressor is located in the back.(if you have load leveling suspension) which is on the driver side, inside the van at the back. The hitch was added later to my van (by the previous owner) and thats where the little pigtail snakes out of the plastic through the grates there.