Low oil pressure mind boggled

Hello! Thank you guys for having me here! I'm a complete noob but still learning as much a I can. I own a 2006 yukon denali and my heart lies in this model. I'm having retarded issues with low oil pressure an I can't understand it for the life of me. I would greatly appreciate if somebody could point me in the right direction. The Car currently has 180k mileage done and I've slowly been restoring it. Everything has even running fine for the last 4 months of purchasing it. Inclusive of things I've changed. I've changed te solenoid valves, water pump, shock absorbers, done rust proofing, new tires / rims etc. After everything suddenly one day after all these months the oil pressure gauge dropped and the idiot light and warning tones came out full beeping. Only when I rev it goes back up but not to the 275 marker. Just to the quarter marker before it. (I'm assuming each marker is 37.5 psi?). Anyways I've now replace the oil pump, the oil pressure sensor and another oil switch all from AC Delco. There admit any knocking noise to what I keep reading. Engine runs quiet. Replace the gaskets, cleaned out the entire oil pan and from timing cover etc. Replaced the oil filter change the oil. Started the car up it jumps up to the first little marker and stays there. When I rev or drive normally it goes steady to 75psi the fat quarter marker. It only gives me this light and beeping noise when I sit idle in traffic or t a red light. It's so frustrating. I've to shift into neutral and keep revving. No matter what I've done everything is still the same. I've cleaned and replaced everything I can think of. Is it the oil I'm using? Ever since I did an oil change it went stupid. Do I have to replace my whole engine? I know high mileage engine pressure drop happens. Any suggestions? I would truly be grateful truly. Is It the oil filter?. I can't figure this out, even the mechanics are bogged and trying the same things. I love you guys!

There is no knocking or ticking noise whatsoever. Sorry for this autocorrect crap.

Is the oil pressure sending unit the same as oil pressure sensor? If I start up the car and sit idle it's completely fine sitting on the first marker, no stutters or engine noise nothing. This only happens when I idle in traffic after driving then everything goes apeshit in the car with te warning alarms and lights etc meh.

Yes done the compression tests no codes. Thank you for responding Mik! I was getting worried there. I'll try again today at another garage for pressure check. Also when I turn the key to ON but not start the engine. All the gauges move. Except the oil pressure gauge. It just sits at 0

Housing oil? What is that? Sorry little sheepish I feel

At I ask is the oil pressure sending unit and the oil pressure sensor the same thing? So many confusing people saying yes and no to this. If it is then I replaced a sensor and a switch. If not then I'll get a search for a sending unit.

Anybody?

I meant using not housing, sorry. Compression test is test done seperate from codes, u know that right? Are cylinders reading correct pressure? When oil light goes on is rpm's dropping real low, ready to die low? If so could be idle control sensor. Go to rock auto.com and enter the sensors u have a question about, c if they come up different. They should b the same. Is your engine filled to correct oil level? Is the dipstick OK, not damaged and maybe giving u an off reading? Jus throwing ideas out there. Did u do something wen u changed the oil to cause it?

Oh wonderful!!! Yes I haven't got any codes and I'm not gettin any pressure issues from the test. I haven't had the light go of with all the driving I did today. Next time it drops I will be sure to check the rpm when light goes on to have a clear answer!. The oil level is filled correctly but I will check the dipstick and the oil level again just to be sure again for the enth time. All I did was change the oil and oil filter and when my DIC said oil health at 89% is when this happened. I'm using the correct that is written in the car manual. The oil filter also I've changed again and using the one for this specific model cause I opened it up and it wasn't dirty or trashed. Maybe it's the oil viscosity? But I think you're right it might be a sensor issue or an off reading. I will check and let you know thank you so much truly for the ideas I grately appreciate it.

Turn the ignition on to the position before start, press the accelerator three times within 5 seconds then turn the ignition back to off .. Wait and start..

I too have an 2003 Yukon with the same symptom of the oil pressure dropping and the alarm goes off and the oil gauge goes to zero. I purchased my Yukon in July with 207,000 miles it now has 225,000 and just started the problem with the oil pressure dropping to zero. What I have noticed is this problem only happens when the temperature has dropped to under 60 degrees outside. This means that the air conditioner compressor doesn't come on which means it doesn't put a load on the engine to keep the engine running around 700 rpm. I also found that if the problem occurs I will pull off the road and shut the engine off for a couple minutes restart the engine runs fine at an idle. This tells me it may be a sensor or the throttle body that controls the low engine idle. the significance of the air conditioner running is that it forces the engine to run at an higher rpm. I would just like to know which part is bad so I don't get stuck paying for parts I don't need.

@guruXB5RL this might be the same thing happening to me. Earlier when I was driving I realized the heat wouldn’t come on and then 10 mins later low oil pressure.

Ok these all had recalls on the filters you need to go get a acdelco filter. Also at the back of the driver side is a oil pressure sensor it has a built in screen that just snaps on it pull the sensor out remove the screen and reinstall and let me know

I own an auto repair shop in Arizona. Every time we've seen low oil pressure on a GM V8, replacing the o-ring on the oil pick up tube has taken care of the issue. We've probably done about 10-12 of them over the last 6 years. Same thing happened on my wife's '08 Yukon Denali. Started getting low oil pressure and a slight knocking noise at idle. Replaced the o-ring and it has run another 30,000 miles since then with no issues. She has 181,000 miles on it now. Its like a $5 part from the dealer. They always have them in stock.

I also have this problem it idles at 40 then slowly starts dropping down to i say maybe 20. Then after a while code P0011 comes on. Replaced sending unit with ac delco, replaced phaser with ac delco, replaces cam sensor and actuator, replaced oil pick up o-ring, no longer has a oil pressure sensor screen yet oil pressure drops and i get this code

I have a 2008 Yukon doing the same thing. Starts fine, 40 psi oil pressure, then drops down with ticking noise. Replaced oil sending unit/sensor. Convinced it's the o ring on the pick up tube. Seems too big a job, so inquiring at local places to change. First place quoted over $900. Seems pretty steep (he said 8.5 hr job.). Can anyone suggest what this o ring replacement job should cost? Thanks