1997 Chevy c/k1500 owner's manual refers to 7 wires for trailer hookup tucked under rear frame of truck. I could only find 5 wires. Yellow, brown, dark green, light green, and a heavy gauge white. I used a probe and the left directional signal works on yellow and the right directional signal works on a green. Nothing else seems to work. All lights on the truck work. Anybody have any suggestions? Thanks. P.S. This site and all its contributors are fantastic.