Toyota Tundra Blinking 4hi Solved.

I have a 2011 Tundra that has the same scenario of the 4hi light blinks all the time and 4 wheel drive doesn't engage. When this started happening about two years ago it had the same symptoms as many others on this forum have talked about. When cold it would work fine until I drove a few miles, then shut off engine and started it again. The 4 wheel drive would no longer engage until next day then it would do the same thing. I tried several things, even replaced the A.D.D. with no luck.
Finally I started tracing the wiring harness and found one of the plugs wasn't plugged in good.
After plugging it in right, everything is working great. Hope this helps someone else with this issue.

 

Cool. Which plug was it?