On a sierra it goes up inside drivers A piller, accross roof and into the boot lid and finally down near the boot lock to a signal amplifier, I expect the S2 is the same

Check amp in boot lid is not dead, and do a end to end test on cable as they break near the boot hinge

I fitted a MK4/5 (cant remeber which) escort ariel to my old sierra

http://www.chippers.me.uk/sierra/aerial/aerial005.jpg