Hello all. I am rather new to the ls swap world. I had a shop in the Bay Area do my swap 4 years ago. My transmission grenaded so i took it out. I took it to shucks a premier tranny shop in the Bay Area. They rebuilt it and I installed it.

everything worked normally prior to the transmission issue. I literally pulled it out and put in the rebuilt transmission. The only thing that’s different is i haven’t hooked up the wires bc i don’t know which pins.

my shift selector switch was wired up and i stupidly didn’t take photos. It was a bad wire job by the shop anyways. No harness just crimps on the pins.

engine and tranny 2006 l33 5.3 with a 4L65e transmission - i can provide the vin

i have no idea where to start. I have 2 wires i need to wire into the pigtail i bought.

i believe one wire runs to the rear lights. I have no idea what the other wire did.

 

By "shift selector switch" I assume the switch (sometimes) mounted on the side of the transmission. Your first pic is very out-of-focus and presumably the connector for this switch.
This switch enables the reverse lights and implements the "Park/Neutral Safety Switch" to prevent a dangerous engine start while in Drive or Reverse. It may do more on some models, but nothing critical; it DOES NOT control shifting of the trans.
Several different switches have been used. A part number or at least a clearer photo might help someone here tell you which pins are used for what.

Your second picture shows two heavy gauge wires; I suspect they are supposed to connect to the Park/Neutral Safety pins on the switch. One wire goes to the ignition switch, the other to the starter solenoid.
If you want to just get the car started, you can short those two wires together.