Most of these cars came with the wire even though the changer didn't come as an option. It goes from the headunit all the way into the hatch. It's black, about a 1/4" thick. It travels along the passenger side of the car and should stop behind the passenger side panel in the hatch.

In the headunit side it plugs into this..I believe..

o.o.o.o
o.o.o.o
o.o.o.o
.....o

And the hatch pins look like this..

.....o
..o...o
o...o...o
..o...o

It's extremely important that the pins are NOT dirty.

Let me know if you have a clean one.