under the seat is the plugs for the seat. unplug them and start poking around in there.black wires are round most of the time, so start with a ground. then poke around till the seat moves, hold the seat switch so you know its getting power where you need it.

that torx is also a 15 mm bolt head, but they are a kinda tall bolt. could keep working each sides bolt and lift the back of the seat up to keep the bolt off the seat bottom. open end wrench may do the trick.