Originally Posted by
blindsquirrel
Control Module Voltage is, most likely, the voltage at the control module.
Whether that's measured the same way on a Chrysler or a BMW or a GM or a GM with a P59 or GM with an E67, and at which pin, I guess it depends.
Since we don't live in fantasy land and our electrical conductors are made of plain dumb copper and not magical room-temperature superconductors, every wire that carries current will have some amount of voltage drop between the source and the load. The smaller the wire and the higher the current, the more the voltage drop along the way. So voltage at the source (battery + post) and the load (in this case, whichever one of the ECM power pins is being monitored) will not be the same. Lots of wire and connectors and relays and ignition switch contacts getting in the way.