Not sure but I don’t believe there is an ECU Power supply unit as such.
Electrical power is provided by the battery and the alternator when the engine is running and is known as B+. The alternator output is controlled by the BMC which manages charging of the calcium lead acid battery. B+ is what I believe is fed to the ECU.
The ECU itself may massage B+ to create 5V levels used by some sensor, maybe...
Edited to add that the above is relevant for VE and VF. VZ may be even simpler.
