GM Moving Oil Pressure Regulator Location and New Pumps

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The reason I put this in the Engine Oil Filter thread is that GM has specified higher bypass valve pressure differential settings due to this new innovation. I have attached the TSB from 2017 describing it.

I have seen mentions of lower than expected oil pressure from these later GM V8s. Also total loss of indicated oil pressure due to a code that sets for low oil pressure. This problem is apparently fixed by replacing the filter.

Anybody know if this setup is still being used? The TSB covers 2012-2017, has it continued thru 2020 into 2021?

I have a 2020 6.0L V8 that will not build up oil pressure by just cranking. The engine has to be running, and it takes a couple of seconds for pressure to show on the gauge. When I do an oil/filter change, I prime the engine by cranking 10 seconds in flood clear mode. Should be enough to get all the air out. I usually see the gauge start to get pressure around the 10 sec. mark. But with this engine I'm not seeing that. FWIW, this engine came from the factory with a PF-48, with the lower bypass pressure.

Any thoughts?

Edit: Be sure to read the TSB.
 

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Considering that GM has been indicating a zero oil pressure when oil pressure was merely low (& throwing a low oil PSI code), I wouldn’t be surprised if pressure was actually present. Ford does the same thing (at least on the Grand Marquis in my sig it does), no oil pressure indicated under “flood cranking” conditions (to prevent my dry startup chain rattle).
 
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Interesting. They want the oil to be filtered even when cold vs the filter being in bypass.

But now we have GM TSB's misusing the tolerance vs clearance phrase.
 
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Looks like the fram XG10575 should cover it. Bypass 16-28. Gm spec 22psi.

Wix WL10255XP will cover it too. 22 psi bypass.
 
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The reason I put this in the Engine Oil Filter thread is that GM has specified higher bypass valve pressure differential settings due to this new innovation. I have attached the TSB from 2017 describing it.

I have seen mentions of lower than expected oil pressure from these later GM V8s. Also total loss of indicated oil pressure due to a code that sets for low oil pressure. This problem is apparently fixed by replacing the filter.

Anybody know if this setup is still being used? The TSB covers 2012-2017, has it continued thru 2020 into 2021?

I have a 2020 6.0L V8 that will not build up oil pressure by just cranking. The engine has to be running, and it takes a couple of seconds for pressure to show on the gauge. When I do an oil/filter change, I prime the engine by cranking 10 seconds in flood clear mode. Should be enough to get all the air out. I usually see the gauge start to get pressure around the 10 sec. mark. But with this engine I'm not seeing that. FWIW, this engine came from the factory with a PF-48, with the lower bypass pressure.

Any thoughts?

Edit: Be sure to read the TSB.

You're mis-reading the bulletin.

The only thing a new filter "fixes" is a problem caused someone spinning on the wrong filter:
The PF64 and PF63, which is commonly confused by many in the automobile service industry as an ACDelco® PF48 and/or PF48E , because both oil filters have the same appearance and oil can size. However these oil filters are not the same and have different internal bypass valve opening pressure specifications (PF48/PF48E = 15 PSI (100 kPa), PF64/PF63E = 22 PSI (150 kPa).
Let me translate in 2017 language:
Technician, stop thinking you know which filter belongs on these engines. You obviously don't know. If you did, we wouldn't need to write this bulletin. From now on, actually have your parts guy look up and get you the correct filter. Ya'll have been using the PF48 and PF48E because that's what previous generations of these engines used. The filters may look the same but they aren't. The engines use different filters now. Stop spinning on PF48s!

The bulletin specifically covers Gen 5 V8, 2nd gen HFV6, SGE, and LGE. Yes, the engines and their filter requirements still apply in 2021. The bulletin hasn't been updated with the new model year because it's likely not a problem anymore. With all the engines now being in production for at least 5 years, techs have figured out which filter goes where and aren't spinning on the wrong one.

Your 2020 6.0L is a Gen 4 V8, not a Gen 5. Your 6.0L uses a PF48.
 
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ZeeOSix

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The way I read the TSB is that the filter bypass valve opening pressure was increased because the oil pump pressure regulating sensor is now located farther away from the pump in the newer GM engines. Increasing the filter bypass pressure helps ensure that the filter doesn't go into bypass during the short time that the engine is first started in cold conditions and the oil pressure starts to regulate at the oil pump. With the old fashioned oil pump design, the pump output pressure is controlled almost instantly at the pump, but with the new oiling system design the pump could lag in its response to control the pump output flow/pressure.

This new functionality should actually send more initial oil volume at start-up into the filter and oiling system until the pump starts becoming controlled/regulated by the main gallery feedback sensor. Once the system starts regulating the pump pressure, it should operate as usual. I don't see how this could cause a lack of flow or oil pressure at the sensor, nor how the filter could cause the lack of flow or pressure compared to an old fashioned oil pump - both should still be positive displacement. What causes low oil pressure is a lack of flow, a pump that is bad, shot journal bearings, a pump that isn't being controlled correctly or a totally clogged oil filter. On a new engine with a new filter on it, if there is low oil pressure (as defined by the service manual) then something is seriously wrong.

Of course, if this is a computer controlled variable volume output pump, then other factors could be involved concerning "normal" operation.
 
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garageman402

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The bulletin specifically covers Gen 5 V8, 2nd gen HFV6, SGE, and LGE. Yes, the engines and their filter requirements still apply in 2021. The bulletin hasn't been updated with the new model year because it's likely not a problem anymore. With all the engines now being in production for at least 5 years, techs have figured out which filter goes where and aren't spinning on the wrong one.

Your 2020 6.0L is a Gen 4 V8, not a Gen 5. Your 6.0L uses a PF48.
Thanks, I checked the engine RPOs covered by that, mine is L96. I have always tried to prime the oiling system after an oil & filter change by cranking, but in this engine I can't get any pressure reading. Even after cranking in "flood clear" mode for 10 sec or more, then starting, it still takes a few seconds to show pressure on the gauge. No noises are present, but the engine is still new with only 6669 miles. I was wondering if a new oiling system was causing this. I've also read about "2 stage" oil pumps? Anyone know of th
The only thing a new filter "fixes" is a problem caused someone spinning on the wrong filter:

The "changing the filter" I was referring to was another issue that "might" have been related to this system change. Loss of pressure has been reported, setting a code that apparently defaults to a zero gauge reading. Shutting down and restarting restores gauge operation until another low pressure incident triggers another episode. Changing filter (and presumably oil) reportedly "fixes" the issue. Some have found the O-ring on the oil pickup tube cracked and sucking air, reducing flow (and resulting in pressure loss).

Of course, if this is a computer controlled variable volume output pump, then other factors could be involved concerning "normal" operation.

Maybe the variable volume output pump is the cause of that issue?
 

garageman402

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The way I read the TSB is that the filter bypass valve opening pressure was increased because the oil pump pressure regulating sensor is now located farther away from the pump in the newer GM engines. Increasing the filter bypass pressure helps ensure that the filter doesn't go into bypass during the short time that the engine is first started in cold conditions and the oil pressure starts to regulate at the oil pump. With the old fashioned oil pump design, the pump output pressure is controlled almost instantly at the pump, but with the new oiling system design the pump could lag in its response to control the pump output flow/pressure.

This new functionality should actually send more initial oil volume at start-up into the filter and oiling system until the pump starts becoming controlled/regulated by the main gallery feedback sensor. Once the system starts regulating the pump pressure, it should operate as usual. I don't see how this could cause a lack of flow or oil pressure at the sensor, nor how the filter could cause the lack of flow or pressure compared to an old fashioned oil pump - both should still be positive displacement. What causes low oil pressure is a lack of flow, a pump that is bad, shot journal bearings, a pump that isn't being controlled correctly or a totally clogged oil filter. On a new engine with a new filter on it, if there is low oil pressure (as defined by the service manual) then something is seriously wrong.

Of course, if this is a computer controlled variable volume output pump, then other factors could be involved concerning "normal" operation.
Does my L96 have the computer controlled variable output pump? Would this explain no pressure while cranking? Those pumps you mention, are they still positive displacement?

I unintentionally confused the issue by combining two questions/issues in one post, my apologies.

The low oil pressure issue was discussed in a 3 year old post, and I thought I'd start a new thread to bring it back to the forefront. No resolution was reached in the older thread. I thought maybe the new system outlined in the TSB may have contributed to the issue.
 
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Does my L96 have the computer controlled variable output pump? Would this explain no pressure while cranking? Those pumps you mention, are they still positive displacement?

I unintentionally confused the issue by combining two questions/issues in one post, my apologies.

The low oil pressure issue was discussed in a 3 year old post, and I thought I'd start a new thread to bring it back to the forefront. No resolution was reached in the older thread. I thought maybe the new system outlined in the TSB may have contributed to the issue.
Your L96 is a flex fuel capable version of the LY6.They are both Gen 4 engines and did not get the variable pressure oil pump. Only the Gen 5’s got that such as the 5.3.

4B0CD9E9-13A0-416D-951D-F43FC145FFDE.jpg
 

ZeeOSix

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Even though it doesn't have a variable volume oil pump, it sounds like per the TSB that it still uses a remote pressure sensor to control the oil pump output pressure. If that's the case, then it's probably computer controlled in some manner. Would have to see the factory service manual to verify.
 
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Even though it doesn't have a variable volume oil pump, it sounds like per the TSB that it still uses a remote pressure sensor to control the oil pump output pressure. If that's the case, then it's probably computer controlled in some manner. Would have to see the factory service manual to verify.
The OP has a L96 engine. The TSB does not include the L96. It’s just a simple Gen 4 engine. It has a pressure sensor at the top of the manifold near the firewall, but it does not have any computer control of the oil pump pressure.
 
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What the article I referenced above mentions is the oil pump relief valve spring had problems on some, stays open. I would be concerned if it seemed my oil pressure rises too slowly on a new 2020 under warranty, even if the vehicle was made after the Aug 28, 2019 cutoff date.
 
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