An electrical system architecture for a vehicle brake by wire system provides three electrical power sources: an electric generator, an electric power storage device such as a battery, and a third source which may be either an electric generator or storage device. An electric circuit has a common node and (1) connects the first electric generator to the common node through a first diode, (2) connects the first electric power storage device to the common node through a second diode, (3) connects the electric power source to the common node through one of the first and second diodes, and (4) connects the common node to the electric power inputs of control unit through circuit breaker devices. A sub-circuit within the electric circuit interconnects the first and second diodes, the common node and the first and second circuit breaker devices and isolates them within a zone protected from short circuits to points outside the zone. Voltages across the diodes are checked when the first diode should be reverse biased and again when the second diode should be reverse biased to detect circuit faults such as short or open circuits.