cheverolet sells an aftermarket tow hitch wiring kit
i bought it from cheverolet, and it made for several truck model including the titan. Its about 30 something dollars and plugs directly into the plug under the bumber and has a 4 and 7 pin connector built in
just fyi if anyone is looking for one
also i have tow relay 1, 2 for sale brand new never opended for 40 shipped.