[greg64]

Greg, the light green wire is the backup light hot wire. Just checked my schematic. Brown is tail, yellow and dark green are the turn/brake lights. The chassis is used for ground, that's why the ribbon cable has 4 wires and not 5.

The yellow wire in post 1408 should have power whenever the ignition is on.

Incidentally, with the truck not running, you should be measuring 12.6V if the battery is fully charged. 11.something means your battery is low.

If you want a feel good moment, try running a test wire from positive on the battery to the light green wire at the transmission switch connector. This should turn on both backup lights.

You know, the power side goes through a fuse in the fuse box, according to my schematic (and memory). Try probing both sides of this fuse with the key on. Should be 12 on both sides.