One side of the injector connector goes to 12V plussitive. The other end, in pairs, goes to the EEC for grounding (two injector drivers).
Injectors are NOT part of the 5.00 VDC sensor system. Could be a low battery (and bad charging system), wiring issues between the ignition switch and the plus power to the injectors, injector wiring harnesses, etc.
Personally, if I didn't know the condition of the ignition switch, I would suspect that before the injector harness. I've not seen those harnesses go bad as often as the ignition switch.