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Oil Pressure gauge P0521

29K views 21 replies 5 participants last post by  Olita1 
#1 ·
I have a 2008 5.3L with the flex fuel. I noticed the other day that my oil pressure gauge would run at about 40psi whit crusing but under braking it would fall to 20. Then once I got to a complete stop it would dip to around 10psi then return to 20. In my way to work this morning the CEL came on but the DIC didn't say "Service Engine Soon" or anything. I ran the CEL and got error code P0521. And ideas, help or suggestions would be great.
 
#12 ·
I would get a manual gauge and check the oil pressure. If it is fluctuating like that with a real gauge, I'd suspect you are having mechanical problems in the engine (possibly a defective bypass in the oil filter housing or pressure relief valve in the pump).
 
#13 ·
Trying an oil change to see it that helps. I have around 7,000 miles since my last one (Mobil 1 and Mobil 1 filter). Hoping it is just dirty oil. I threw a cab of Seafoam in it to let it run through the engine for a day or so. I've already seen a little improvement. I'm hoping its just gunk clogging the screen on the oil pump and that the Seafoam, oil change, and this Lucas oil treatment clears it up. Otherwise its off to the dealership with her.
 
#14 ·
I hope you do not have so much gunk in the pan to clog the oil pickup. That would mean taking the pan and pickup tube off for cleaning. If that is the case, you'll probably need new bearings as well. I would not think that would be covered under warranty. surely you change your oil more ofthen than to allow for that kind of build up.
 
#17 ·
Just got done with the oil change. The old stuff was black. Just put in conventional, with the Lucas oil treatment, just in case I had to do it again. Everything is back to normal. My OLM said I still had about 35% left. I made sure to mark my mileage so I can change it every 3,000 from now on.
 
#19 ·
BigRedZ71 said:
Well I bought this truck used about 5 months ago, so I've only changed the oil once. I hoping this Lucas oil additive in conjunction with the Seafoam clean it up. Otherwise whatever the problem is won't be an easy, or cheap fix.
I am having the same issues no oil pressure showing check engine light is on and the AFM is in 8cyl mode only any suggestions?....I have had the upper part of the motor rebuilt twice due to valves being shot from the Oil consumption problem and the oil pan and pickup replaced.
 
#20 ·
I had about the same problem and I figured out what the problem was and fixed it. First I changed the oil pressure switch and screen and still had the same problem. I discovered that the main problem was the oil filter. If you look in the filter and the core in the middle is plastic, that is no good. That is considered a free flow filter from people that work in the factory that makes them. One of the problems is the the holes in the plastic is so big that paper can blow through them and get in the engine and I don't have to tell you how bad that is. Dealerships seem to be using the AC Delco filter and they are all plastic core. Find a metal core filter and put it on and change the oil. Keep that filter you take off the truck just in case you have engine problems and find out there is paper in the engine. This has been the fix for this, the computer keeps thinking that the oil pressure is low for the rpm's and that is why it keeps giving the error. And you may want to know why are they making plastic core filters. That is a simple, the whole system is an automated line and it can make 180 filters per min. It all comes down to the dollar. Hope this helps and quit having the dealership change your oil.
 
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