has to be located on dash not sure what stye dash you have but look on right side of dash just where center consdole ends should be right there also some had just a plug in for ipods on top of dash center
are you sure the truck is equipped with a aux connector? not all cars have them, most of the new ones do, but an 04 it may not, if it doesnt just buy and aftermarket car stero with an aux connection and its on the dash.