$35 Electric Power Steering with Fail-Safe - No eBay module and no caster issues!!!

And that is the issue with with doing a mod that is based on hacks applied to salvage yard parts. Tech support is limited.
A couple of ideas
1) try sending a pm to the guy that started this post back in 2016
2) look around on line for a wiring diagram for a 2009 Prius and verify that the wiring is correct.
3) if the wiring is correct, look on line for a shop Prius service manual that has trouble shooting for their electric power steering units.
4) is it possible that the power steering unit that you got was damaged and is defective, see if the yard that you purchased from will swap it for a different unit.