Low oil pressure (5.3)

[08 denali]

Im having the low oil psi. Its showing the po521 code. When I start it up it shows 40psi whether its cold or warm. Then within mins it falls to zero. I replaced the sensor and cleared the code. I didn't even half to drive it before it started doing the same thing on the startup. I have a snap on scan tool and when I check the oil pressure on it when it drops it shows 2PSI. When I shut it down it still shows 2PSI. I need to get this handled asap. I just bought it from a dealer a few hrs away from where I live and hes willing to work with me on it. I got a good deal on the number side of it. Engine sounds as it should not even the slightest tick. Its a 08 with 125k on it any help would be greatly appreciated.

 

[IllogicTC]

Im having the low oil psi. Its showing the po521 code. When I start it up it shows 40psi whether its cold or warm. Then within mins it falls to zero. I replaced the sensor and cleared the code. I didn't even half to drive it before it started doing the same thing on the startup. I have a snap on scan tool and when I check the oil pressure on it when it drops it shows 2PSI. When I shut it down it still shows 2PSI. I need to get this handled asap. I just bought it from a dealer a few hrs away from where I live and hes willing to work with me on it. I got a good deal on the number side of it. Engine sounds as it should not even the slightest tick. Its a 08 with 125k on it any help would be greatly appreciated.

Well let's start with five common questions:

Is there the proper amount of oil in the engine?
Is the oil still good? (Not black or dark brown, don't just go by Oil Life Monitor when you first bought it)
Is the filter in good shape? As in, freshly-installed as part of the dealer's getting it ready for the lot or your receiving the vehicle?
Does the engine oil have anything alarming in it? It shouldn't look muddy brown, it shouldn't have yellow crap coming up with it on the dipstick, no metallic shavings, etc.
Is it the proper weight of oil for the 5.3 V8? You can reference the owner manual to see what kind you need.

 

[IllogicTC]

And then we can get a little more advanced:

-Is your oil filter bypass valve stuck?
-Is the replacement sensor junk? (By the way, a p0524 is specifically low oil pressure, 0521 is Engine Oil Pressure Sensor/Switch Range/Performance
-Is your oil pump producing proper volume?
-Is the ENTIRE wiring circuit leading to/from your oil pressure sensor intact, and not shorted or open? And all connectors properly cleaned and seated?

 

[08 denali]

And then we can get a little more advanced:

-Is your oil filter bypass valve stuck?
-Is the replacement sensor junk? (By the way, a p0524 is specifically low oil pressure, 0521 is Engine Oil Pressure Sensor/Switch Range/Performance
-Is your oil pump producing proper volume?
-Is the ENTIRE wiring circuit leading to/from your oil pressure sensor intact, and not shorted or open? And all connectors properly cleaned and seated?

fresh oil and ac delco filter and bypass valve working proper. it is the 0521 code showing. Id hate to think the sensor is bad but I do know its possible. I don't know much about the pump... the wiring looks good. now bare with me as Im no mechanic just a parts swapper but should the sensor be wet with oil when I remove it. Thanks for the input keep it coming PLEASE....

 

[IllogicTC]

Wait, is this an I6 or a V8?

In that case, it's very likely that a wire's bad somewhere. The sensor isn't a sensor at all on the I6 - it's a switch! Literally just a switch, that gets pushed closed (completes the circuit) at 12psi. The readout on the dash is a complete fabrication by the PCM! So instead of acting like a sensor, where you'll get variable voltage (think like an O2 sensor acts), it's either no/low voltage, or high voltage. Just on an off, 1 and 0 in binary terms.

Could you fill out the vehicle section of your profile? It'd help a bit.

There should be just two wires running to it, right? One's purple and one's tan/black. Both run to the PCM, which is the blocky thing next to your intake manifold with three big wiring connectors plugged into the side of it. Check those wires along the whole length! They may be melted and shorting out somewhere, or grounding out someplace where they've rubbed up against something or come out of their loom. Also check the actual connector that seats into the switch and make sure it's not burnt out or anything.

As for oil on it... I'm not sure. I would think it comes in direct contact with the oil, so having oil on it would then be okay.

 

[08 denali]

Wait, is this an I6 or a V8? Pretty sure it's the I6, V8s only came in the XL/EXT...

In that case, it's very likely that a wire's bad somewhere. The sensor isn't a sensor at all on the I6 - it's a switch! Literally just a switch, that gets pushed closed (completes the circuit) at 12psi. The readout on the dash is a complete fabrication by the PCM! So instead of acting like a sensor, where you'll get variable voltage (think like an O2 sensor acts), it's either no/low voltage, or high voltage. Just on an off, 1 and 0 in binary terms.

Could you fill out the vehicle section of your profile? It'd help a bit.

There should be just two wires running to it, right? One's purple and one's tan/black. Both run to the PCM, which is the blocky thing next to your intake manifold with three big wiring connectors plugged into the side of it. Check those wires along the whole length! They may be melted and shorting out somewhere, or grounding out someplace where they've rubbed up against something or come out of their loom. Also check the actual connector that seats into the switch and make sure it's not burnt out or anything.

As for oil on it... I'm not sure. I would think it comes in direct contact with the oil, so having oil on it would then be okay.

it is a 5.3 for sure.

 

[Blckshdw]

Wait, is this an I6 or a V8? Pretty sure it's the I6, V8s only came in the XL/EXT...

Careful, you might trip Roadie's misinformation detector with that one...

 

[IllogicTC]

it is a 5.3 for sure.

Ah, I see, they kept the 5.3 around up through the last year, just used the LH6 instead of the LM4. My mistake, the shop manual for 2008 on here only shows 4.2 wiring. In that case, have a look at this:

Engine code p0521 - Ask the GM Technician - GM-Trucks.com

Apparently there's a filter for the valve lifter area, separate from the "regular ol' oil filter," likely to help protect the DOD/AFM components. Apparently it can get gummed up and cause conditions such as this.

 

[IllogicTC]

Careful, you might trip Roadie's misinformation detector with that one...

No worries brah, I'm generally self-correcting. And besides, dude knew what's up that he's got a V8. Which doesn't surprise me, because c'mon, Denali package! Posted a link that may help.

 

[08 denali]

No worries brah, I'm generally self-correcting. And besides, dude knew what's up that he's got a V8. Which doesn't surprise me, because c'mon, Denali package! Posted a link that may help.

Im gonna check on that filter first thing in the am. I pulled the sensor again and it was dry

 

[08 denali]

Im gonna check on that filter first thing in the am. I pulled the sensor again and it was dry

Ok so heres how my day went. I pulled the valve lifter filter and the bottom was pretty dirty so I cleaned it up and hooked mechanical guage up and boom 42psi and after running for about 45min it never fell below 33psi. So I take it for a spin and 45min into the ride I noticed it starting to drop and after about a hr of driving it was back to zero and the light was on to turn engine off. So I figured it was clogged again so I pulled it and yes it was dirty but not as bad as the first time. Cleaned it up again and put it all back together and let it run for about 1/2hr and checked temps and they was down to 13-15range and holding there. I was convinced the oil was contaminated and went to change it so I drained it and pulled the filter(no biggie) Went to install the ac pf46 and it wouldn't go on at all by that time the only place open was Walmart so I went and got a fram 3506 and that wouldn't go on either. So Im stuck like chuck with no oil filter. Once the fluid was changed I was gonna hook it up to the mechanical guage again. I inspected the old filter which went right on and it was a Autolite AL10060 which is not anywhere on the list. I googled it and it comes up as a fuel filter. Which filter are you guys using? Ive never seen anything like this

 

[Blckshdw]

According to this cross reference website, your filter is an oil filter, the AC Delco equivalent part number is a PF64, not PF46. Or you'd need a Fram PH10060 instead.

 

[08 denali]

According to this cross reference website, your filter is an oil filter, the AC Delco equivalent part number is a PF64, not PF46. Or you'd need a Fram PH10060 instead.

Ok I got the filter straightened out and put new fluid and filter in. I left the valve lifter filter out and put sensor in and started up(46psi) I let it run for 35min and went and checked it and it was down to 17psi. I took sensor out and hooked the mechanical guage up and it was right on with the sensor. It was 17psi at idle at 2k rpm (49psi) and and 3k rpm (55psi). Has anyone dealt with it this monster

 

[C-ya]

Looking at the latest numbers, it looks normal. Higher at startup (thicker oil), gets warm and thins a little, so the pressure drops at idle and rises as rpms rise. May just need a couple of good flushes to get the crap out that is plugging the filter.

BTW, where is this filter? I'll check mine at the next oil change.

 

[08 denali]

Looking at the latest numbers, it looks normal. Higher at startup (thicker oil), gets warm and thins a little, so the pressure drops at idle and rises as rpms rise. May just need a couple of good flushes to get the crap out that is plugging the filter.

BTW, where is this filter? I'll check mine at the next oil change.

17psi seems low at idle I think. I called the local dealer and spoke with a tech and he said it sounds like worn out oil pump and its gonna need a engine soon. Still hoping it could be something simple. The filter is located under the oil pressure sensor on the top of the backside of the block. Just fish it out with a pick. What kinda numbers are you guys seeing that's able to monitor the pressure?

 

[Texan]

Looking at the latest numbers, it looks normal. Higher at startup (thicker oil), gets warm and thins a little, so the pressure drops at idle and rises as rpms rise. May just need a couple of good flushes to get the crap out that is plugging the filter.

BTW, where is this filter? I'll check mine at the next oil change.

Look at the link in #8. Scroll down and it shows the filter.
I agree with you comment about the psi's, look normal for 100,000 miles.

Does the instrument panel gauge operate like the one on the I6?

 

[The_Roadie]

V8 has a real analog sensor, so the gauge doesn't lie the same way as the I6. (If it's like the ECT gauge, it lies a little due to filtering and non-linearity).

 

[djthumper]

Sounds like someone didn't keep up with proper oil changes when needed or filled it with crap. I would get a new filter, oil and flush to flush that crap out like C-ya mentioned. I would probably let it run a little longer than normal to help get it out and clean that filter again.

 

[strat81]

If that lifter filter keeps getting clogged, I'd suspect sludge. Have you considered pulling the valve covers to see what's what? If the valve covers are sludged, I'd clean them manually. Then I'd run an HDEO like Delo, Delvac, or Rotella along with a pint of Kreen, and change all that out after 500 miles.

If that lifter filter keeps getting clogged, then there's a chance your oil pump pickup is/was getting clogged too. Kreen may help dissolve some of that.

Why HDEO? HDEOs often clean better than their PCMO counterparts. They also tend to be on the heavy side. The higher viscosity will counteract the thinning of the Kreen, and can also help with oil pressure issues. 15W-40 will most likely be the cheapest, but 5W-30, 10W-30, and 5W-40 are also available. Since my recommendation is to dump it quickly, I'd skip the synthetics and go with 15W-40 if you're in a warm area or 10W-30 if you're in a colder area.

 

[08 denali]

If that lifter filter keeps getting clogged, I'd suspect sludge. Have you considered pulling the valve covers to see what's what? If the valve covers are sludged, I'd clean them manually. Then I'd run an HDEO like Delo, Delvac, or Rotella along with a pint of Kreen, and change all that out after 500 miles.

If that lifter filter keeps getting clogged, then there's a chance your oil pump pickup is/was getting clogged too. Kreen may help dissolve some of that.

Why HDEO? HDEOs often clean better than their PCMO counterparts. They also tend to be on the heavy side. The higher viscosity will counteract the thinning of the Kreen, and can also help with oil pressure issues. 15W-40 will most likely be the cheapest, but 5W-30, 10W-30, and 5W-40 are also available. Since my recommendation is to dump it quickly, I'd skip the synthetics and go with 15W-40 if you're in a warm area or 10W-30 if you're in a colder area.

Well here is an update. After a few oil changes and replacing valve lifter filter Im idling at 39psi and going up to 62 depending on driving of course. Im hoping I don't deal with that issue anytime soon. Just goes to show how proper vehicle maintenance is critical. Just simple fluids and filters. Thanks to everyone that had input with my issue. Now its time to tackle the steering wheel sensor(again) I put a new one in lastnight but I think I missed a critical part at the end of the process.

 

[chicagotransam]

V8 has a real analog sensor, so the gauge doesn't lie the same way as the I6. (If it's like the ECT gauge, it lies a little due to filtering and non-linearity).

Off topic, but I had a bad pressure switch (pegged gauge at 80psi). I replaced it with a Standard switch and now it drops to zero every time I key up my CB radio... lol

Just so everyone knows, buy OEM!

 

[sarg]

As another aside, had 2 cases if oil filters causing this, one fram and one Bosch on 2 different vehicles.

 

[warriorpluto]

Same problem op was having. I'll pressure would go down after a couple minutes of driving. Had code p0521 changed sensor and filter that goes under it from dealer. No change. Changed oil. Oil pressure is now good with driving and not going down but now hot idle is now between 20-25lbs. Cruising pressure is 40-50lbs. The low hot idle is what scares me now. Used to be close to 30lbs or a little over. When I drained the oil I didn't see anything. Where I pulled the oil pressure switch filter it has a little black sludge on it so I put the one on i got from the dealer today. I'm thinking this engine is slowly going down. Has 180k on it now. Has anyone ever had any problems with the relief in the oil pan? Also since this year lh6 is 24x the engines are over 2k so what if I got an engineharness from an 07 envoy and pcm and drop in an engine with 58x? Would it work?

 

[mrrsm]

If your Vehicle VIN sports the Number “3” in the 8th Digit… these are the normal, nominal Oil Pressures you should be seeing at various engine speeds when the engine is HOT and operational ... and without other mechanical problems involved to interfere:

24 PSIG @ 1,000 RPM
35 PSIG @ 2,000 RPM
38 PSIG @ 3,000 RPM

With so many miles on your engine… If you think that the Oil Pressure Sensor needs to be changed… changing out the GM Lifter Valve Oil Screen Filter underneath it right along with installing a Brand New Oil Filter and Fresh Motor Oil should also be done at the same time. This series of videos have Good Instructions and Visuals to aid you in doing this uncomfortable job... with a few extra tricks thrown in for good measure.

Here is the Screen GM Part Number:



...and for the Oil Pressure Sensor:

GM Part No.: 12616646

SENSOR, Engine Oil Pressure/Temperature


Having Moderate Mechanical Skills are the order of the day here… mostly because when encountering the difficulties evidently involved here… Experienced Folks are less inclined to become discouraged when things start to get hard and they have to rely on “working blind” ...and trust their actions to fix these problems...without being able to actually SEE what they are doing:

Part I:

Part II

Here is another Instructional Video on the R&R of the Oil Pressure Sensor … just to give you another look of “How to Go At It …in order to Get At It”:

And ...What The Hell… One more look at How to Do the Job with a Few More Tricks won’t hurt:

If after doing these actions ...your Oil Pressure keeps dropping… using an Engine Oil Flush Procedure would be next... and if that fails to solve the problem.,.. the Last Place to investigate the problem is a Failing Oil Pressure Pick-Up Tube Seal where it bolts to the base of the Gerotor Oil Pump… or by a “Sticky Oil Pressure By-Pass Valve” in the pump as previously mentioned… But First things First and we’ll keep our fingers crossed for you.

 

[warriorpluto]

Well I did all of what you mentioned last night except for a flush. I'm kinda scared to do that. My oil pressure now doesn't drop below 20lbs anymore since I changed all those things last night. But at idle it hovers around 20-24lbs hot idle. Cruising oil pressure is good for now. I'm thinking of dropping the pan and cleaning out out and do a new oil pump and pick up with new pressure relief valve in oil pan. I'll drive it around today and update this thread later

 

[Mooseman]

Dropping the pan on these trucks is a bitch so it's not a trivial thing.

I just had the exact same issue with mine with the P0521 code. Pressure looked OK (mine is in metric so ) and I still had over 40% oil life left on Rotella T6 5w40. When I deleted my DoD in Sept, I replaced the oil pressure sensor as a preventive measure. I also replaced my oil pump with a new Melling standard replacement pump. Initial startup I ran it on cheap dino 5w30 which I then immediately replaced it with another new filter and the Rotella. My oil pressure "looked" lower than before the job. It never used to go lower then halfway but now it did on hot idle. I just figured it was the new sensor. There is also no more lifter filter.

Fast forward to this month, I get the P0521 just before I have to get an e-test . Swap the old sensor back in, reset codes, same deal. Oil level was fine, just dark. Changed the oil and filter, code gone.

I figure the oil pump is not as good as the original or the bypass is not to spec. @warriorpluto , in your case, I would suspect a worn pump and/or bypass, a leaking oil pump pickup o-ring or the engine bearings are just getting worn.

 

[mrrsm]

Yes… I saw that you mentioned replacing the Lifter Valve Filter as well… but I wanted to flesh it out because with so many views of this topic already, it has developed a kind of “persistence of memory” that others might still be looking at regularly ...and so far... the OP's topic does not have the “Step By Steps” at hand as to how to do this work. As for the question about Engine Flushing … there is one cool video from “Briansmobile1” Youtube Channel that might boost your confidence as he properly performs an Engine Flush:

How to Flush the 5.3L Engine:

Although this next Guy suffered a complete failure of Oil Pressure and yours seems less likely to be this serious… his video shows the two causes for this to happen and what he did to repair his 6.L Engine.... and the principles still apply to the Smaller V8s sharing this Oil Pump Design. As diagnosed by @Mooseman 's insights ...there were early problems with the Oil Bypass Valve which.... contrary to popular thought... actually gets a lot more action than people might think; especially around the time that the Oil Filter starts getting a bit clogged.

The first design of the Gerotor Oil Pump was allowing the Spring-Loaded Cylinder inside the Oil Pressure Relief Valve to get STUCK IN THE OPEN POSITION… which has the same effect as if the Oil Pump had failed. He covers this very scary subject quite nicely here with some novel solutions to avoid the need to remove the Crankcase Oil Pan to R&R the Gerotor Oil Pump.

The only thing to be added to his re-positioning idea... is to have several small, telescoping Magnetic Pick-Up tools placed just inside the pump area on the blocking rags stuffed inside when using the Dremel Cut-Off Wheel in order to capture as many of the Steel Particles from the Oil Pick Up Tube as possible and prevent contaminating the Crankcase and internal Rotating Engine Assembly with fine, Ferrous Metal Particles and Disc Dust.:

Gerotor Oil Pump Issues and Mods:

 

[jonest3]

For future readers like I was, I had the same issue with low oil pressure (both the gauge and the code P051) and fixed it with a new oil pressure sensor, lifter valve filter (found below the sensor once removed), and an oil change. I however did not need to undo/remove anything at all (fuel lines, PCV hose, brake vacuum, etc.) I just reached behind the block, unhooked the sensor, and put a 27mm deep well socket on it with a U-joint attachment and extension.

Not contradicting what others have seen, maybe my 2006 just had more access than other models. But in case it's a problem for you I'd estimate this takes less than 30 minutes to fix (if faulty sensor/clogged filter is indeed your problem).