That's correct, when the ignition is in the ON position, the fuel pump relay should activate power to the BY wire. Be sure to check if the LR wire is reading 12V - this is the power from the fuse box that the relay provides to the BY wire. If the LR wire reads 12V when ignition is on and you're getting 0.14V from the BY wire, it's probably a bad fuel pump relay. If the LR wire is not getting 12V, check the fuse at MB-9. I would check this stuff first before checking grounds.