So when I bought my 91 XJ it already had a hitch and 7 way plug on it and when I ask for the build sheet from jeep it showed it had a tow package also. Right away I noticed the 7 way plug was broken and corroded
Hitch:


Old 7 way plug

So I went to the local autoparts store and bought a new 7way plug
New plug

I then disconnected the wires from the old one to new one, and used my 7 way tester to see if they were working. Only 12v. and the tail markers were working, i then followed the wiring to inside the jeep were it plugged in into this connector that brakes off from the main harness
​​​Connector

I then disconnected the trailer harness from the connector to see if any pins were broken off or it had any kind of corrosion, but all of them were good. I then took my digital test light to see if I'm getting power on the pins. And just like plug only the 12v power and the tail markers were working, no breaks, or turn signals.

So I ask you jeep masters of this forum were should I go next? Or should I just bypass this and use a after market harness?

 

Try testing before the connector. Use those sharp pointy needle type probes on a multi meter or with the sharp pointy end of your test light. The plug on the vehicle side of the wires could be bad.

 

OK so I went behind the connector on the vehicle side and again only the 12v power and the tail maker light wire wore working, all the other wires were not showing power when turn signals or brakes were used. The 12v was red wire and the tail markers was a blue and red wire.

 

Then the problem could be anywhere upstream.
Not sure how easy it would be without some diagram of where to hook up but probably easiest to get some new 7-wire trailer cable and just reroute the whole thing.