Hi Nanpean and
to the forum.
Unfortunately, I have no specifications for the original Hall Sensors fitted in the GM motors, But the specification for the Honeywell SS41 Hall sensors that are commonly used as replacements states that they can work with a voltage of between 4.5V min and 24V max.
If you already have a 12V supply, it might be safer to add a
12V to 5V DC/DC converter to provide the correct +5V supply, this should ensure that it won't cause further problems with other components on the controller's circuit board
(like the USB programming interface chip) that may be linked to the same +5V supply.
Alan