Auto Trans "hold" light?

Okay, let me first say i'm new here and probably posting this in the wrong spot for that i'm sorry. I have a 91 B2600i 4x4 with an auto tranny and the A/T temp light comes on when cold and then just goes on and off all day and the "hold" light and function kicks itself in and out all day? Do I need a rebuild or a sensor, what? Any help would be great, my wife also said the truck tried to put itself into 4x4 the other day when she drove it? Possible??

Sounds like something got wet.

Yep that's what I was thinking ! Flood history? Teenage son borrow n go creek hoping? Give us little history on truck!