Automatic transmission won't down shift from highway speed to city

What is your question?

When coming out off highway speed to city speed transmission isn't shifting down, and what happens is that when i accelerate again from a complete stop i here my rear end differential knock hard (like its still it top gear). I'm thinking i need a senor replaced in the transmission, again no code is showing during diagnostic. but if i turn off my truck let it sit for a minute or two the transmission works normal and shifts properly (its like its resets). Any other ideas? could it be a wiring issue?