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Discussion Starter #1
Just noticed while on the highway, at about 75mph and 2200 rpm my oil pressure is reading about 77 psi. Sitting at idle I'm at about 58. I THINK I'm used to seeing this about 10-15 psu lower. I did just get an oil change and I suppose it's possible they put something like 20w50 in but I really doubt it. It is possible that after having this truck for 10 years this might be the first time I really noticed it, and maybe it's normal. If not, any idea what could be causing it? I have a 6-hour work trip tomorrow and don't feel like getting stranded.

This is an '07 NBS 5.3 with the cylinder deactivation, 173k on the clock.

Thanks,
Darel
 

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That's on the high end they could have the wrong filter and the sending unit telling you the oil is trying to pump through mismatched holes or something
 

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Discussion Starter #3
Crap. There's nothing I can do for a week and about 2000 miles because of this work trip next week.
 

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Solid axle '01 Tahoe/'03 Sierra/'18 Silverado
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What's more likely is these engines have a horrible issue where the sending unit's oil passage builds up with gritty sludge.

Clean oil helps move around the gunk and so oil changes can cause the reading to change.

At some point, GM started putting a thimble-shaped screen under the sending unit to prevent the gunk from actually entering the sensor. I can't recall the year they did that. My 2003 didn't have it.

New sensors come with this screen, so even if you truck doesn't have one. You can add one.

If you have the screen you can pull it out and clean it. But getting the sender out is enough of a chore that i think it worth it to put a new one in while I'm at it.
 

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Discussion Starter #6
Thanks guys! What I may do is see if I can run the truck through a quick lube maybe on my way out to ohio. I also just noticed a lifter tick when I first start it, after this oil change. It's not unusual for the truck to tell me it's due for one, by ticking, but it's never done it right after a change.
 

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So I dropped the truck off last night with a note. They got it in first thing this morning and re-changed the oil, verifying weight and filter. No issues there. Started it back up, same problem, 65 at idle, 80+ at anything over 3000 rpm. They were at a loss. I need to get on with my day so I figured I'd roll the dice and get on with my trip. If it died, I'd just leave it and rent a car on the company dime.

However, finally, a clue. Driving home from the shop just now it threw a CEL for faulty oil pressure sensor. Yay! I am assuming, since the gauge is still fluctuating like normal, just at the wrong end, the resistance is off. I can worry about that in a week or two and I feel fine driving it now.

Thanks for your help.

D
 

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Mmm Sandwich
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I mean that would have been the first thing to check and don't take anything to that shop again if they couldn't figure that out

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Except that it hadn't thrown a code until I was driving home from the shop. So thanks for the helpful input.
 

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Mmm Sandwich
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If the shop needed a code to solve the problem they are shit

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Discussion Starter #11
I just asked them for a second oil change and to verify the filter and oil viscosity. I pulled the code. I don't let shops work on my cars other than oil changes.

By way of an update, I made it to ohio. Oil pressure kept gradually climbing until it never got below 80. Then right around the PA border it dropped to 0 completely. No noise, no knocking, kept going. Consistently pulling multiple codes for the sender (0501, 0503 etc) so I'm happy leaving it go until I get around to replacing the sender.
 

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Interesting thread & it appears as if your problem is solved. I would have thought that dirt in the sender would result in a false low reading & prior to this I was under the impression that when a GM OP sensor failed completely you got a pegged out high reading whenever you had electrical power to the system. But, that's why I come to this site--to learn.

Anyway, I did change my OP sensor on my '02 (with 5.3) at around 170k because I had the throttle body & intake manifold off to change knock sensors. I was not having any problems with it (at least I THINK it was reading accurately), but when you have the intake off you have real easy access to it, so why not. With that typed, I had to buy an EXTRA deep (it was 1 & 1/16 or 1&1/8", I cannot remember off hand) socket from AutoZone, because the 1/2" drive deep socket in that size that I already owned was not deep enough. I would also say that changing that OP sensor with the intake & throttle body on looks like it might be a bit of a bitch.
 

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Mmm Sandwich
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They usually fail and show no pressure bit anything electrical can go the other way too.

Op dont put the screen back in when you replace it

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I don't remember looking for a screen on the replacement OP sensor that I bought, but it was an AC Delco from Rockauto, so based on your previous post, I assume it had one. I threw the old one away, even though it was functioning fine. If I ever had to go through the work that changing another one would entail, I am damn sure not putting used parts on. On an aside, I did change my head gaskets on that truck last spring. I've used Mobil1 full syn since she was a baby, & I was really happy about how clean things looked undernath the valve covers. Not even a hint of sludge.
 

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They usually fail and show no pressure bit anything electrical can go the other way too.

Op dont put the screen back in when you replace it

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Just to clarify, are you advising OP to take the screen out of the new sensor if it comes equipped with one?
 

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Mmm Sandwich
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Just to clarify, are you advising OP to take the screen out of the new sensor if it comes equipped with one?
No I am telling him to take the screen out of the oil pressure port the sensor threads into. They are known for clogging up

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Ah, okay. I didn't read all the answers carefully enough. When I did mine, I don't think mine had a screen in the port in the block, but then again, I wasn't really looking for it at the time.
 

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Mmm Sandwich
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Ah, okay. I didn't read all the answers carefully enough. When I did mine, I don't think mine had a screen in the port in the block, but then again, I wasn't really looking for it at the time.
Yea because yours is an 02

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