My dads truck had the shift cable snap this morning so we had to install another one. There is a plug in the steering column that it plugs into, and if its plugged in the truck will not shift [shifters locked].. but if its unplugged it runs perfectly fine.. and shifts fine..
Any clue what this is?

Its kind of an L shape. or like a corncob pipe if you will haha.. it has a like thinner line like ___[] then the [] has a metal oval in it and a thing that pushes in and out.. haha.. sorry my explanation sucks.. I can try to take a picture of it later..

 

 

It's called the shift interlock soleniod, it's what keeps you from shifting out of park without pushing the brake, from what you describe it's working opposite the way it's supposed to. It needs to be adjusted to work properly.