I am using Yaris non-ABS ECU with Prius column. It will not work with any other column. I am using pulse generator for now and later will add pulse generator from the reluctor wheel on my Ford 8.8 which will gave me variable speed dependent assist.
Waid
Tested one more EPS / ECU that works in fail-safe/limp home mode with fixed level of assist. 2008-2011 Scion XD
2008-2011 Scion XD It's almost identical to Prius. The Prius, Yaris and Scion Xd ECU share same exact plug and works with each other.
ECU Part Numbers that function in fail-safe /...
The Corolla and Prius ECU will work but there is a little circuit board that you will need as well. This board is built in to the Saturn Vue ECU. The upper steering shaft is same on Saturn Vue and Toyota therefore it will easier to just swap the whole thing out.
The Toyota Yaris is the smallest and the next size up is the newer Nissan Versa that I have not tested but will to bet that it will work in Fail-Safe as well. The problem is the smaller the EPS, the smaller the plastic driven gear and may not take the load of a bigger car. Worst case the gear...
The motor is not noise at all. In fact, I don't hear at all. Almost all new small to medium cars has column electric power assisted steering. It uses a steel worm gear with very hard plastic gear that is very smooth. While sitting up, you can not see the motor.
Electric assisted power...
In order to convert my hydraulic power steering rack to manual, I took the valve out, removed the sleeve and tack welded the input shaft to the pinion shaft.
YouTube Videos:
DIY Electric Power Steering 1 - EPS with Fail Safe
DIY Electric Power Steering 2 - Bench Test
DIY Electric Power Steering 3 - Mounting Options
DIY Electric Power Steering 4 - In Car Test