Do you know where this switch or sensor could be?
Heres what iv did to my car.
first i ran my power cable though my Firewall Gromet, Striped it , Connected a fuse. Then i Ran the power cable to the boot, Next i removed the center console and proceded to splice the cables inorder to add both my remote cable and a Hi-Lo converter to an the OEM harness. once that was done i ran the RCA on the opposite side of the car and connected it to the Hi-Lo converter, wired the Rca to the back and connected it all up.
If you need pictures i do have some to post.