Not that this will necessarily help, but here is a link to the directions for overriding on the factory system...
http://elcova.com/groupee/forums/a/tpc/f/6706011751/m/9...891088431#9891088431
And, here are the override instructions for the dvd speed restrictions (which grounds the parking brake wire on the dvd system):
http://elcova.com/groupee/forums/a/tpc/f/6706011751/m/1.../199106444#199106444