5.3 low oil pressure

[Drummerboy84]

I have a 2007 Chevy Tahoe LT 2wd with the 5.3 flex fuel. The day I bought her (April of 2016) I was 2 hours into the 4 hour trip back home when the "low oil pressure shut down engine" came on. Of course I panicked and pulled off, checked oil level, called the guy I bought it from, and prepared for the worst possible news. He assured me it still had pressure but just needed a new sensor.... Cut to pulling into my driveway.... Bought a new switch, the 1-1/16" socket to turn it, and built the perfect dual 6" + swivel tool combo to get to the damn thing. Swapped it out (took me close to 1.5 hours) drove around the block and same light comes right back on.... #&$@! Phoned a knowledgeable friend who told me most people forget or don't realise there's a screen under the sensor.... Well shoot, my new unit didn't come with one so I guess I'll go buy one, replaced the screen and oil pressure was good for another 1-2 months.... Yup, it F#&$ING happened again but this time while towing a trailer to a different state.... So knowing that my sensor was good and the screen was pretty fresh still I took it to whatever local jiffy lube was near and asked them to do a flush treatment (motor medic or something like that) and since that day I have never experienced low pressure again. Until new years eve a few days ago while completely loaded and heading to an out of town gig. I pulled over, checked oil, waiting around for my heart to mend and the engine to cool and started her up and oil pressure came back. Dropped a few more times there and one more time on the way home. Going to go through the motions again today and run motor medic, change oil, swap in a new pressure sensor, and replace the screen. I'm half tempted to remove the screen altogether although I'm not sure if that would cause a leak or do some sort of damage although I've since helped friends replace their sensors and found they don't have a screen (older models). Hope this helps someone. Sorry for the novel. I'll attempt to update in the following weeks as to whether it worked again or not.

 

[Fless]

How often are you changing your oil, and what oil and filter are you using?

 

[iamdub]

I have a 2007 Chevy Tahoe LT 2wd with the 5.3 flex fuel. The day I bought her (April of 2016) I was 2 hours into the 4 hour trip back home when the "low oil pressure shut down engine" came on. Of course I panicked and pulled off, checked oil level, called the guy I bought it from, and prepared for the worst possible news. He assured me it still had pressure but just needed a new sensor.... Cut to pulling into my driveway.... Bought a new switch, the 1-1/16" socket to turn it, and built the perfect dual 6" + swivel tool combo to get to the damn thing. Swapped it out (took me close to 1.5 hours) drove around the block and same light comes right back on.... #&$@! Phoned a knowledgeable friend who told me most people forget or don't realise there's a screen under the sensor.... Well shoot, my new unit didn't come with one so I guess I'll go buy one, replaced the screen and oil pressure was good for another 1-2 months.... Yup, it F#&$ING happened again but this time while towing a trailer to a different state.... So knowing that my sensor was good and the screen was pretty fresh still I took it to whatever local jiffy lube was near and asked them to do a flush treatment (motor medic or something like that) and since that day I have never experienced low pressure again. Until new years eve a few days ago while completely loaded and heading to an out of town gig. I pulled over, checked oil, waiting around for my heart to mend and the engine to cool and started her up and oil pressure came back. Dropped a few more times there and one more time on the way home. Going to go through the motions again today and run motor medic, change oil, swap in a new pressure sensor, and replace the screen. I'm half tempted to remove the screen altogether although I'm not sure if that would cause a leak or do some sort of damage although I've since helped friends replace their sensors and found they don't have a screen (older models). Hope this helps someone. Sorry for the novel. I'll attempt to update in the following weeks as to whether it worked again or not.

The screen is for the AFM engines, so it won't be on a pre-'07. The AFM system is really sensitive to sludge/gunk, so it has a screen at the point where oil is fed to it. If it's getting clogged, you're either running crap oil, running it for too long or your engine has sludge/gunk/crud that is incrementally working loose or all of the above. Removing the screen will allow any particulates to reach the tiny passages in the AFM system, potentially causing a much more serious failure. Don't remove that screen. Clean or replace it.

It could be the oil's viscosity drastically changing from temperature. Long trips and higher loads will increase engine operating temps and, therefore, engine oil temps. Synthetic oil is more stable at holding its viscosity, so that might help. What you might have is a split O-ring in the pickup tube. Thermal expansion coupled with wildly varying oil viscosity could be why this is an intermittent issue.

Next time it happens, with the vehicle parked on a level surface, be sure the oil level is at the "full" mark on the dipstick. Add two quarts of oil and park it with the front of your Tahoe in a nosedive, like pulling forward into a ditch or reversing onto a hill. See if the oil pressure suddenly climbs back to normal range. Drive back to level ground and rev the engine to around 1500 RPM and see if the low oil pressure returns. If so, it's gotta be a leaking pickup tube O-ring. Drain the extra two quarts and plan out the repair.

Also, if sludge, etc. is a factor in your engine, you don't wanna run any harsh detergents to quickly break it up and flush it out. The chemicals breaking up the deposits in larger chunks can cause more problems since these larger particles are circulating through the system. They can clog the screen and/or the filter and/or the lifters, etc. You need to slowly and gradually dissolve the deposits so they're removed during a routing oil change. The mild additives and detergents in quality oil does this. I highly recommend synthetic oil if you don't already run it. It might seem more expensive up front, but you can run it twice as long and it retains its operational and protective properties for much longer than conventional. Now, if your engine is, in fact, dirty on the inside, then I'd suggest running a quality cheaper conventional oil and changing it when it gets dirty, regardless of the mileage. ALWAYS use a good filter. You might end up changing it every 2-3K. But, it should start to go longer and longer before it turns really dark. That's the stuff being dissolved, suspended and then drained in the oil, cleaning out your engine.

 

[OR VietVet]

@iamdub beat me to it. The 2 quart overfill and check it should tell you something but if problem is that intermittent, you may be waiting a while. Since you are a "pro" at getting to the sensor area, I would attach an oil pressure gauge and have a long enough hose on it to tape to w/s and watch the pressure. I assume you have decent pressure since you have not complained of engine noises.

I forgot, is there a way to attach a Tech 2 and see oil pressure? Someone will chime in and educate me. Your problem seems so intermittent that I would do the full synthetic oil change as recommended by @iamdub and what @Fless is alluding to. I personally use Mobil 1 and a WIX filter.

 

[Larryjb]

What was the condition of the oil itself?

I had trouble with oil pressure going low on me, especially half way through oil change intervals. It took awhile to convince me to check for a coolant leak in the head because I never got any "chocolate milk". After I finally removed the valve cover I finally way the leak. I also got a sample of my oil tested which confirmed the coolant in the oil, but also confirmed there was no other engine damage. An oil test may give you clues as to what is going on.

A slow leak will allow the water to be removed from the oil via the PCV, but the ethylene glycol remains in the oil and reacts with the oil creating a sludge. This sludge would plug up my oil filter giving me low oil pressure.

 

[iamdub]

@iamdub beat me to it. The 2 quart overfill and check it should tell you something but if problem is that intermittent, you may be waiting a while. Since you are a "pro" at getting to the sensor area, I would attach an oil pressure gauge and have a long enough hose on it to tape to w/s and watch the pressure. I assume you have decent pressure since you have not complained of engine noises.

I forgot, is there a way to attach a Tech 2 and see oil pressure? Someone will chime in and educate me. Your problem seems so intermittent that I would do the full synthetic oil change as recommended by @iamdub and what @Fless is alluding to. I personally use Mobil 1 and a WIX filter.

A Tech2 or any other scanner would just display what the pressure sensor is reporting. This would be good for determining if the gauge in the instrument panel was faulty, though.

 

[donjetman]

A common problem is a bad o-ring on the oil pump pickup tube in the oil pan. Over fill it by 2 qts and point the frt of the vehicle down hill and see if pressure improves. Don't drive it overfilled.

 

[RBUser]

I have a 2007 Chevy Tahoe LT 2wd with the 5.3 flex fuel. The day I bought her (April of 2016) I was 2 hours into the 4 hour trip back home when the "low oil pressure shut down engine" came on. Of course I panicked and pulled off, checked oil level, called the guy I bought it from, and prepared for the worst possible news. He assured me it still had pressure but just needed a new sensor.... Cut to pulling into my driveway.... Bought a new switch, the 1-1/16" socket to turn it, and built the perfect dual 6" + swivel tool combo to get to the damn thing. Swapped it out (took me close to 1.5 hours) drove around the block and same light comes right back on.... #&$@! Phoned a knowledgeable friend who told me most people forget or don't realise there's a screen under the sensor.... Well shoot, my new unit didn't come with one so I guess I'll go buy one, replaced the screen and oil pressure was good for another 1-2 months.... Yup, it F#&$ING happened again but this time while towing a trailer to a different state.... So knowing that my sensor was good and the screen was pretty fresh still I took it to whatever local jiffy lube was near and asked them to do a flush treatment (motor medic or something like that) and since that day I have never experienced low pressure again. Until new years eve a few days ago while completely loaded and heading to an out of town gig. I pulled over, checked oil, waiting around for my heart to mend and the engine to cool and started her up and oil pressure came back. Dropped a few more times there and one more time on the way home. Going to go through the motions again today and run motor medic, change oil, swap in a new pressure sensor, and replace the screen. I'm half tempted to remove the screen altogether although I'm not sure if that would cause a leak or do some sort of damage although I've since helped friends replace their sensors and found they don't have a screen (older models). Hope this helps someone. Sorry for the novel. I'll attempt to update in the following weeks as to whether it worked again or not.

Did you get this resolved yet?

I've been battling this issue since I bought my 2012 Avalanche LTZ this past summer. The oil pressure switch/sender/sensor was replaced by the dealership that previously owned it in 2020. Then, when I was in the process of test-driving it, the check engine occurred again, so they had it replaced again. I then drove it the 1 1/2 hour home and around for a week or so before it happened again.

I figured at this point that it was obviously NOT the sensor itself and thought it could be a wiring or connector causing the issue. This time, when I brought it to a local dealership, I asked them to replace the connector as well. They only did a quick voltage check, supposedly changed the sensor again, and "called it a day." The check engine code occurred again within a week or days.

After doing some research that mentioned that the little filter screen gets gunked up easily and could cause the issue, I replaced the sensor myself, and although I had bought a new filter screen, decided to leave it out to see what happened. It went a few more days without the error code, but now it happens every time I actually drive it, never when it's just idling in the driveway.

During more research, many forums mentioned the oil pickup tube and the o-ring. Some seemed to say it resolved their issue, but one guy detailed replacing everything mentioned in that forum string, then after spending $$$ on all that, he said he had the connector replaced and never got the error again. So I bought the connector with pigtail, but have yet to install it since it's so difficult to get to without taking off the intake manifold per the official GM procedure.

Supposedly, the dealership I bought it from had just done the oil pan and I believe they did something with the o-ring and pickup tube, but now cannot find that documentation--not even in their meticulous CarFax maintenance records. (Curiously, the replacement of that pressure sensor also disappeared from the CarFax records, so I edited it and added it back in.) Anyway, that's why I didn't believe it was the oil pan/pickup tube/o-ring fix, but now am starting to wonder after hearing and reading how that tends to make this error code happen.

Any thoughts from the experts here?

 

[Geotrash]

Did you get this resolved yet?

I've been battling this issue since I bought my 2012 Avalanche LTZ this past summer. The oil pressure switch/sender/sensor was replaced by the dealership that previously owned it in 2020. Then, when I was in the process of test-driving it, the check engine occurred again, so they had it replaced again. I then drove it the 1 1/2 hour home and around for a week or so before it happened again.

I figured at this point that it was obviously NOT the sensor itself and thought it could be a wiring or connector causing the issue. This time, when I brought it to a local dealership, I asked them to replace the connector as well. They only did a quick voltage check, supposedly changed the sensor again, and "called it a day." The check engine code occurred again within a week or days.

After doing some research that mentioned that the little filter screen gets gunked up easily and could cause the issue, I replaced the sensor myself, and although I had bought a new filter screen, decided to leave it out to see what happened. It went a few more days without the error code, but now it happens every time I actually drive it, never when it's just idling in the driveway.

During more research, many forums mentioned the oil pickup tube and the o-ring. Some seemed to say it resolved their issue, but one guy detailed replacing everything mentioned in that forum string, then after spending $$$ on all that, he said he had the connector replaced and never got the error again. So I bought the connector with pigtail, but have yet to install it since it's so difficult to get to without taking off the intake manifold per the official GM procedure.

Supposedly, the dealership I bought it from had just done the oil pan and I believe they did something with the o-ring and pickup tube, but now cannot find that documentation--not even in their meticulous CarFax maintenance records. (Curiously, the replacement of that pressure sensor also disappeared from the CarFax records, so I edited it and added it back in.) Anyway, that's why I didn't believe it was the oil pan/pickup tube/o-ring fix, but now am starting to wonder after hearing and reading how that tends to make this error code happen.

Any thoughts from the experts here?

It's possible to nick that o-ring on the install just enough for it to suck some air. I know because I did it. It's also possible to install the wrong o-ring. There are at least two different ones for the LS engines, and the thicker one is for the truck engines.

If I were facing your dilemma and the pigtail didn't work, I would drop the pan myself, change the o-ring the right way with the right part, along with the oil pressure relief valve in the pan, and see where I'm at with oil pressure. And I would also put that screen back in if I were planning to keep the AFM system intact because it will keep grit out of the VLOM oil passages.

After that, you have relatively few possibilities: 1/ the cam thrust plate seal 2/ the cam bearings 3/ the oil pump itself including the integrated pressure regulating spring 4/ the barbell at the back of the engine 5/ the VLOM manifold itself.

 

[OR VietVet]

If do what @Geotrash suggests, make sure to clean that pickup screen/tube.