CEL error P0521

muddy tires

Original poster
Member
Dec 5, 2011
63
2005 Trailblazer EXT 5.3L V8 with about 260,000 km. My wife got an error on the DIC about low oil or low oil pressure. She checked at the dipstick and it was very low (which is a bit unusual as it never burns oil). She added about 2L then I added about another 2.5L to get it into the hash marks on the dipstick. Today her check engine light came on with a code of P0521 which seems to be Engine Oil Pressure Sensor/Switch Range/Performance. I've cleared the code and i'm going out for a drive to see if it comes back.

Could the low oil have set the CEL? Could a faulty sensor switch have caused an oil leak? Anybody have any hints on the next steps on my diagnostic journey? I must admit that oil leaks and pressure problems scare me.
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
That's getting up there in miles. How long since anybody last checked the level? How long since it was changed? 4.5L is a HUGE amount to be low unless it's dripping on the highway and you don't see it, or it's being burnt. You need to start checking it MUCH more diligently, and keep records. Like weekly.
 

muddy tires

Original poster
Member
Dec 5, 2011
63
Thanks Roadie. I'll take my 10 lashes with a wet noodle :sadcry:

My wife is usually good about checking oil levels but I guess got a little lax. She has it changed when the oil life monitor gets low and it's at about 7% now (she'll have it changed probably after the holidays). I agree that it's a lot of oil and out of character which is concerning. But there are no puddles on the driveway and no obnoxious clouds of black smoke. It passed the Drive Clean (emissions test) this past summer.

So where do i go from here?
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
Keep it filled and pray. I don't know of a thing you can do now to reverse the possible damage, or even measure it. Additives may or may not be useful, but I don't believe in most of them so I have no experience. That's like 8000+ miles without her checking the level? That's what Mrs. Roadie would do to her vehicles, but I know that and just silently check it for her.
 

CaptainXL

Member
Dec 4, 2011
2,445
If its not burning any oil then its probably leaking out the rear main seal. I would get it checked out at a trusted mechanic before the motor burns up. You can look underneath with a flashlight and i bet its wet all the way back to your differential.
 

muddy tires

Original poster
Member
Dec 5, 2011
63
8,000 km tops since last oil change (OLM usually has us in around 10,000). I can't precisely say when the oil level was last checked but I checked it a couple weeks ago when I topped off the windshield washer fluid for winter. Just want to point out that the vehicle hasn't been totally unloved.

I took it out for a short drive (10-15 minutes around our neighbourhood). A message came on the DIC about low oil and to stop the engine. I checked and still lots of oil. When I restarted the error was gone and no CEL.
 

CaptainXL

Member
Dec 4, 2011
2,445
muddy tires said:
8,000 km tops since last oil change (OLM usually has us in around 10,000). I can't precisely say when the oil level was last checked but I checked it a couple weeks ago when I topped off the windshield washer fluid for winter. Just want to point out that the vehicle hasn't been totally unloved.

I took it out for a short drive (10-15 minutes around our neighbourhood). A message came on the DIC about low oil and to stop the engine. I checked and still lots of oil. When I restarted the error was gone and no CEL.

Oil level sender is bad and/or leaking.
 

Denali n DOO

Member
May 22, 2012
5,596
muddy tires said:
8,000 km tops since last oil change (OLM usually has us in around 10,000). I can't precisely say when the oil level was last checked but I checked it a couple weeks ago when I topped off the windshield washer fluid for winter. Just want to point out that the vehicle hasn't been totally unloved.

I took it out for a short drive (10-15 minutes around our neighbourhood). A message came on the DIC about low oil and to stop the engine. I checked and still lots of oil. When I restarted the error was gone and no CEL.

I had that DIC message once and that was the end of the motor. I'm usually down 1-1.5L of oil by 5000km (old motor n new motor), if I pull the trailer I think it gets worse. But 4.5L oil loss in a couple weeks seems like a lot. I'm curios to hear what you find.
 

am-radio

Member
Apr 24, 2012
178
Is it normal for the 5.3 to burn oil? I'm always checking mine and top it up religiously. Usually half a liter to a liter for ever 10,000km, but more when towing.

Please keep us updated on your results. Everyone's problems or issues are learning modules for all of us. Very valuable to the forum family.
 

CaptainXL

Member
Dec 4, 2011
2,445
No its not normal. Considering the previous owner had the water pump replaced the engine probably overheated which could have caused engine damage.
 

am-radio

Member
Apr 24, 2012
178
Possible, but Denali in Doo has a brand engine which burns oil. I'm also running very thin synthetic oil. 0W20
 

CaptainXL

Member
Dec 4, 2011
2,445
Might want to get a subscription to Alldatadiy.com and check TSB's. AFM or DOD is known to cause oil loss in certain vehicles with the 5.3.
 

muddy tires

Original poster
Member
Dec 5, 2011
63
am-radio said:
Is it normal for the 5.3 to burn oil? I'm always checking mine and top it up religiously. Usually half a liter to a liter for ever 10,000km, but more when towing.

Please keep us updated on your results. Everyone's problems or issues are learning modules for all of us. Very valuable to the forum family.

I've rarely had to add oil between changes.
 

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