My father just picked up a 04.5 a couple days ago. We had it in the garage doing some routine maintenance to it. As we finish up he goes to back it out of the garage, puts the truck in reverse and nothing, she just sits there and idles. We shut it off and restart it, it works this time. We put it in drive and it happened again, just idles until we shut it down and restart it.

I'm thinking the APPS sensor is bad?

On the side of his motor, right in front of the air intake horn sits a Black box that is covering up the throttle? When the truck was at idle I could move the lever and it would rev up. Is that where the APPS sensor is? When he bought the truck that Black cover was not there. Maybe some water got into it?