OK, so curiosity got the best of me. I took my truck and unhooked the J wire, and put another in it's place, then ran the wire into the cab and did some road testing with the multimeter. Turns out that the J (cruise engaged) wire puts out a ground when the cruise is set. So I came back to the house and rigged up a light and it works PERFECTLY! You can't make it come on until you've reached the speed that the cruise will set, then it comes on and goes off when the brakes are applied, comes back on when resume is pushed, and goes off when you have it set, but push the coast button, and when you release the coast, it comes back on. I don't see any problems with wiring it this way. Just hook one side of the light to an ignition switched power source, the other side of the light to the J terminal and you're good to go! Guess you can $h!tcan that old diagram I drew up!!
