When I got sick of waiting for an answer to your question:
I don't know the exact path but first thing I'd do would be to strip car's trunk of carpeting. Find where main hunks of wire harness penetrate "firewall" from trunk. Look for promising corresponding location under dash. From trunk gently try shoving a blunted coat hanger in there from various angles (bend end over to blunt). ANY appreciable resistance means STOP! Quit while ahead. If CH passes thru: try to locate it under dash.
May or may not work. If it works: great. If not keep surfing the net for answers. Impt thing is: do NOT force things because you're working "blind."
Give it a shot. Then report back.