Supplemental Information on Pin Assignment in PR3
Checking this document, the Pin 1, 2, 3, 4, and 9 used in PR3 were the same wiring used in iKAGRA.
Also, the motor driver side was also wired this way.
It seems correct to assume that the PR3 is still wired the same as the iKAGRA.
Perhaps the motor driver used in the PR3 exists separately from the PRM/PR2.