Sorry, but you misunderstand the circuits so are barking up wrong trees.
Then the IVR is working.
OK. Lets keep that in mind and see what they may share.
(Check the oil pressure gage conenctor and be sure its not grounding somehow)
Rally dash. Goes along with having oil pressure gage.
That's how the IVR works. It provides an average voltage of roughly 5 V by the bimetal contact opening and then cooling and reconnecting.
video showing the pulsing on an analog meter while bench testing
Please don't do that for more than the briefest period of time! That will burn out the gage.
Put a 10 to 12 ohm resistor on it between the connecting wire and ground. That will simulate a full tank.
