7.3 Godzilla low oil pressure idle
Cargo Master
Joined: Aug 2012
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From: Kaufman TX
Keep in mind Ford's sensors work in absolutes and it's up to the reading device to compensate or not. If you're just getting the raw value from the sensor then you'll see atmospheric pressure for oil pressure when the engine is off. If you do then you need to subtract that engine off number from the engine running number to know real oil pressure.
Logistics Pro
Joined: May 2022
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From: Everywhere and nowhere
Keep in mind Ford's sensors work in absolutes and it's up to the reading device to compensate or not. If you're just getting the raw value from the sensor then you'll see atmospheric pressure for oil pressure when the engine is off. If you do then you need to subtract that engine off number from the engine running number to know real oil pressure.
Cargo Master
Joined: Aug 2012
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From: Kaufman TX
Yes and the sensor reads absolute pressure, not net oil pressure. Not all readers correct for that so it's important to check if it shows 0 with the engine off or not. Someone using Forscan for example will see 14-15 psi of oil pressure with the engine off at sea level because absolute pressure includes atmospheric air pressure.
Mountain Pass
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Logistics Pro
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Cargo Master
Joined: Jan 2004
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From: Minnesota
Yes and the sensor reads absolute pressure, not net oil pressure. Not all readers correct for that so it's important to check if it shows 0 with the engine off or not. Someone using Forscan for example will see 14-15 psi of oil pressure with the engine off at sea level because absolute pressure includes atmospheric air pressure.
More Turbo
Joined: Dec 2003
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From: Park County, CO
Pressure is pressure but flow is proportional to orifice size and pressure difference. Orifice size is just a fancy word for opening size/gap/slot/whatever.
Last edited by ssls6; Dec 13, 2025 at 06:44 AM. Reason: too many words
Cargo Master
Joined: Aug 2012
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From: Kaufman TX
Some readers account for this and will automatically subtract the atmospheric portion and report only working oil pressure. Forscan does not and you can see this when you see 14-15psi of reported oil pressure when the engine is off.
Mountain Pass
Joined: Jan 2010
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Living on earth, we are under constant pressure of 1 atmosphere (atm) or 14.7 PSIA which = 0 PSIG
When you measure 32 PSI in a tire, it is really 32 PSIG which = 46.7 PSIA.
29.92 to 0 in hg = 0 to 14.7 PSIA.
So many sensors are native PSIA so they can read both vacuum and pressure.