Low oil pressure P0521 with PF48 question

Sinyk · February 19

I have a 2012 5.3L LC9 Sierra that has been dealing with the P0521 code for at least a year. When it first appeared, I took it in and the mechanic switched to a PF48 filter from whatever was on there before, and my low oil pressure issues went away. After about 3000 km, the oil pressure dropped again, so I decided to replace the Oil Pressure Sensor with a new GM one. That didn't fix the issue either. Someone told me this could be the oil pick up o-ring, the oil pump, or worse.

Most of my driving is short distances, so the check engine light goes off after a few days, but always comes back.

My question is, would changing the filter from the PF48 to the PF63 increase the oil pressure since the bypass pressure is higher (22 psi vs 15 psi)?

Has anyone done this to fix this issue?

newdude · February 19

Did you replace or clean out the little screen that is underneath the oil pressure sensor?

Seen many of these perform better with the PF-63.

Throw one on and give it a go.

Edited February 19 by newdude

Sinyk · February 19

Yes I replaced the screen under the sensor and cleaned out everything around there that i could.

I'm close to an oil change, so I might as well. Seems cheaper to try that than dropping my oil pan or replacing the oil pump. From what I have read, lots of people have used the PF63 with no issues on this truck/engine.

Edited February 19 by Sinyk

MaverickZ71 · February 19

GM issued a TSB that said using an AC Delco Ultraguard oil filter UPF48R (available at GM dealers, some parts stores. or online) may resolve this situation. The problem seems to happen the most on coldest weather startups. Be sure to use a Dexos-approved 5W30 synthetic motor oil, or equivalent.

From what has been said here, it sounds like the UPF63R may be the best of both worlds, then.

Edited March 10 by MaverickZ71

Sinyk · February 19

The confusing thing is they reissued that TSB multiple times. PIP5276C said to use a UPF48R filter instead of a PF48e, but then they revised it to say don't and just use the PF48, and eventually that you need to replace a ton of stuff due to oil consumption.

Since the PF63 has been used by numerous people for years without trouble, then i probably will start there. I think the UPF63R has a way higher bypass pressure, like 33psi, and the filters are double the price.

asilverblazer · February 19

I had to replace the sensor twice.

Somewhere I recall you can blow out the port it screws in to, I don't remember if it goes to the oil pan or filter, and if the filter had to be off...

Sinyk · February 23

Well I did the oil change, switching to a PF63 and Synthetic 5W-30 Mobil 1. When cold with acceleration, my oil pressure goes up to the 3/4 line. When warm, it sits right around the middle. I didn't drive the truck for a long time this weekend, but so far so good. The pressure was better after the previous oil change with the PF48 though, so time will tell if this holds.

Jworks · March 9

Sinyk, I'm not a mechanic like some on here are, just a guy. I have the same engine and I've noticed it idles differently based on how much its been driven since the last oil change. I've seen my oil pressure down around 21 at idle (after complete engine warmup) and highway driving sits on 38-40. I too quit using the PF48 (which is what the dealers always put on). I've noticed once I change oil the new idle pressure is around 27-30 after warmup. My mechanic said dont worry about it unless it goes down under 20. I think lots of folks with these engines experience this. I use to go by the computer percentage and when it got to around 25% I'd change, but the idle was around 21-22 after the oil got over 3k miles on it. I was advised to keep clean oil in it. After much deliberation and back and forth I decided to do just that. 3-4k miles then change it. I don't go by computer anymore. I just change it at 3-4k miles. I've used the PF63 filter and had no issues. It seemed to provide higher pressure at idle than the PF48. The best idle PSI I ever got was once I paid the way higher price for a more expensive filter rather than the normal PF48 types. That was with a Fram Ultra Synthetic filter. I'm certainly no expert but the higher $ filter does seem to provide higher oil pressure.

Sinyk · March 9

That's good to hear. So far I've noticed with highway driving, my pressure stays pretty well at or slightly under the 275 kPa (40 psi) line. When it's cold it idles above 40 and if i accelerate, it goes up to almost the 3/4 line. When the engine is fully warmed up and idling it looks like it sits closer to 30psi now, not like the 20 or slightly below the 1/4 line it did before. So far I have not seen the CEL return so that makes me happy. I am most concerned about it when camping season comes and I'm towing my RV. I will probably give it another oil change when camping season gets going.