Will the 05-06 tail lights work on a 02-04? If no, why?

 

I think the reverse light is integrated in the later models and separate in the previous, so they aren't interchangeable.

 

I believe that they are almost completely interchangeable (turn signals, brakes, and running lights will all work correctly). The reverse lights in the new taillights will be connected to the rear fog wire of the 02-04. You can make the reverse lights work With some minor electrical modding.

 

I believe rkw summed that one up right. The one thing I miss about the '02-'04 lights is the cheapest cost-nothing mod... rigging up the top fog light bulbs as extra brake lights (if you did not have the fog light capability). Just shape a large paperclip like a staple and connect pins 1 & 4 at the harness.