#1  
Old 10-06-2018, 11:03 AM
Dick Boneske's Avatar
Dick Boneske Dick Boneske is offline
Ultimate Warrior
 
Join Date: Mar 2004
Location: Winneconne, Wisconsin
Posts: 5,159
Default 2008 Grand Prix GXP LS4

I am getting the Service Engine Light often on my GP. The code is P0521--Oil Pressure Sensor Error. I've noticed this is a common problem for the LS4 engines in Pontiacs, Chevs, & Chev/GMC trucks.

Car has 160,000 miles on it. No abnormal engine noises--runs fine, uses about 1 qt. oil each 2000 miles, which is normal for these LS4 engines.

I've replaced the oil pressure sensor and screen below it. The problem still appears within a few days after resetting the trouble code.

Anyone have a likely solution for this problem? .
Attached Thumbnails
Click image for larger version

Name:	2008 GP at Pontiac, IL.jpg
Views:	144
Size:	95.3 KB
ID:	494404  

__________________
BONESTOCK GOATS

'64 GTO Tripower Hardtop (Wife's Car)
'64 GTO Tripower Post Coupe (My Car)
'08 Grand Prix GXP LS4 V8 (Wife's Car)
'09 Pontiac G8 GT 6.0 V8
  #2  
Old 10-06-2018, 12:25 PM
Held for Ransom's Avatar
Held for Ransom Held for Ransom is offline
Ultimate Warrior
 
Join Date: Mar 2000
Posts: 8,518
Default

https://www.obd-codes.com/p0521
Check out the TSB links.

__________________
So long, farewell.
  #3  
Old 10-07-2018, 07:47 PM
Dick Boneske's Avatar
Dick Boneske Dick Boneske is offline
Ultimate Warrior
 
Join Date: Mar 2004
Location: Winneconne, Wisconsin
Posts: 5,159
Default

I have replaced the sensor and screen below it with no change in symptoms. I just changed the oil using synthetic 10w-30 and an AC filter. Oil is exactly on the full mark of the dipstick.

When I reset the code, the service engine light comes on sometimes when starting the engine and sometimes while driving with a warmed-up engine.

Next, I'm going to try taking off the pressure sensor plug and putting dielectric grease on the three terminals.

Any other ideas?

__________________
BONESTOCK GOATS

'64 GTO Tripower Hardtop (Wife's Car)
'64 GTO Tripower Post Coupe (My Car)
'08 Grand Prix GXP LS4 V8 (Wife's Car)
'09 Pontiac G8 GT 6.0 V8
  #4  
Old 10-07-2018, 08:49 PM
Sirrotica's Avatar
Sirrotica Sirrotica is offline
Ultimate Warrior
 
Join Date: Jan 2005
Location: South Charleston Ohio
Posts: 6,014
Default

One of TSBs refers to a DTC PO521 code using another GM/Delco oil filter part #UPF48R. That sounds like a far reach that a different oil filter is going to stop it from setting a code. However it's not going to cost a bunch of money to try it.

Then they talk about the screen in the oil manifold, which I assume is the screen you have mentioned.

There is also talk about doing an ohm reading on the oil pressure switch, which you already say you've replaced, but just because a part is new doesn't mean it's good. I can think of a few times new parts came out of the box defective. Just something worth keeping in mind before you tear your hair out chasing a non problem.

Have you put a mechanical gauge on it to verify what the oil pressure actually is?

A stuck by pass valve, weak or broken relief spring in the oil pump, could also cause it.

Checking oil pressure with a mechanical gauge would show an actual oil pressure problem. Then you have to hunt down the mechanical problem. I would want to verify that the mechanical portion was up to snuff before chasing electrical gremlins.

That's how I would approach the diagnostics, just my .

__________________
Brad Yost
1973 T/A 4 SALE (SOLD)
2005 GTO
1984 Grand Prix

100% Pontiacs in my driveway!!! What's in your driveway?

If you don't take some of the RACETRACK home with you, Ya got cheated

  #5  
Old 10-08-2018, 12:22 AM
Dick Boneske's Avatar
Dick Boneske Dick Boneske is offline
Ultimate Warrior
 
Join Date: Mar 2004
Location: Winneconne, Wisconsin
Posts: 5,159
Default

Good thinking, Sirrotica. I need to figure out where to put a pressure gage so I can determine the real oil pressure.

__________________
BONESTOCK GOATS

'64 GTO Tripower Hardtop (Wife's Car)
'64 GTO Tripower Post Coupe (My Car)
'08 Grand Prix GXP LS4 V8 (Wife's Car)
'09 Pontiac G8 GT 6.0 V8
  #6  
Old 10-08-2018, 08:57 AM
Sirrotica's Avatar
Sirrotica Sirrotica is offline
Ultimate Warrior
 
Join Date: Jan 2005
Location: South Charleston Ohio
Posts: 6,014
Default

Probably a tee fitting between the engine and the sending unit would give you a port for the mechanical gauge, and keep the sending unit operable while running the mechanical gauge at the same time.

If that's not practical because of space limitations, you can buy a spacer called a sandwich adapter, that screws on to the engine and the oil filter then screws on to the adapter. It has threaded ports (pressure and return) that you can tap the mechanical gauge into. They usually come with pipe plugs in the ports so you can choose what port you need to use. The sandwich adapters are used mostly to plumb oil coolers or remote filters into the oil system, but if you were space limited and couldn't use a Tee fitting to tap into between the engine and sending unit, one of these adapters should work fine.

Here's a link to The sandwich adapters: https://www.amazon.com/s/?ie=UTF8&ke...l_7jyovfn4uh_e

I have a Frantz by pass oil filter on my LS2 GTO and use one of the sandwich adapters to plumb it into the system.

__________________
Brad Yost
1973 T/A 4 SALE (SOLD)
2005 GTO
1984 Grand Prix

100% Pontiacs in my driveway!!! What's in your driveway?

If you don't take some of the RACETRACK home with you, Ya got cheated


Last edited by Sirrotica; 10-08-2018 at 09:30 AM.
  #7  
Old 10-14-2018, 11:42 PM
Rocco Testa's Avatar
Rocco Testa Rocco Testa is offline
Senior Member
 
Join Date: Dec 1999
Location: Warwick New York
Posts: 181
Default

If your putting in a pressure switch you will need a special adapter. to run the gauge to, Its metric. A good way that works to do this and is cheap is the use the old sending unit and then drill and tap it to take the gauge .Works great. We had the same problem on are GXP build but after we charge the sender with a new A/C Delco unit, and it was fine. We first checked it with a gauge to make sure we had pressure Hope this helps you.

  #8  
Old 10-15-2018, 10:06 AM
Dick Boneske's Avatar
Dick Boneske Dick Boneske is offline
Ultimate Warrior
 
Join Date: Mar 2004
Location: Winneconne, Wisconsin
Posts: 5,159
Default

Thanks, Rocco. I suspected the LS's may be all metric. Good idea to use the old sending unit for an adaptor.

Your comment about a genuine AC sender is interesting. I don't remember if my replacement was AC--probably not.

__________________
BONESTOCK GOATS

'64 GTO Tripower Hardtop (Wife's Car)
'64 GTO Tripower Post Coupe (My Car)
'08 Grand Prix GXP LS4 V8 (Wife's Car)
'09 Pontiac G8 GT 6.0 V8
  #9  
Old 10-23-2018, 10:54 PM
Rocco Testa's Avatar
Rocco Testa Rocco Testa is offline
Senior Member
 
Join Date: Dec 1999
Location: Warwick New York
Posts: 181
Unhappy

Ya we used the GM A/C brand. Almost twice as much but common on 5.3 motors. to go bad fast. I'm an old school motor guy and builder, my son did the GXP for himself, We did cam, headers rockers, delete the 4 cylinder mode, different intake etc. We also built a bullletproof trans for the car which was the original problem. The car is a nightmare to work on, but super fast. We changed out every part when the motor and trans were out. and I mean every line, hose or sensor. The only one we didn't change was the oil pressure sensor because in was in a spot you could get to easy and it worked before the build. It didn't after for no reason at all.. I don't know if you know this, but one of the knock senors is behind the transmission tailshaft, if it goes bad you will need to pull the trans to get to it, LOL

  #10  
Old 10-24-2018, 10:03 AM
Lee's Avatar
Lee Lee is offline
Ultimate Warrior
 
Join Date: Dec 1999
Location: Seabrook (SE of Houston)/Texas/USA
Posts: 1,884
Default

Do you have a curved aluminum cover, held on with two bolts, right above your oil filter?

If so, it can be removed, then drilled & tapped for a oil pressure source.

There are some aftermarket replacement covers that are already drilled/tapped.

__________________
'73 T/A (clone). Low budget stock headed 455, 222/242 116lsa low-lift cam. FAST Sportsman EFI installed.

'67 Firebird [sold], ; 11.27 @ 119.61, 7.167 @ 96.07, with UD 280/280 (108LSA/ 109 ICL)solid cam. [1.537, 7.233 @93.61, 11.46 @ 115.4 w/ old UD 288/296 108 hydraulic cam] Feb '05 HPP, home-ported "16" D-ports, dished pistons (pump gas only), 3.42 gears, 275/60 DR's, 750DP, T-II, full exhaust (3" w/Dr. Gas X, Xlerator mufflers).

My webpage http://lnlpd.com/home
  #11  
Old 04-26-2021, 01:46 PM
Dick Boneske's Avatar
Dick Boneske Dick Boneske is offline
Ultimate Warrior
 
Join Date: Mar 2004
Location: Winneconne, Wisconsin
Posts: 5,159
Default

Lived with the intermittent oil pressure problem when the engine is cold for three years. No serious problems until yesterday, when a valve train noise (ticking) began. Diagnostic says number one cylinder misfire. Is there anything I can do to determine the actual cause short of tearing the engine apart?

__________________
BONESTOCK GOATS

'64 GTO Tripower Hardtop (Wife's Car)
'64 GTO Tripower Post Coupe (My Car)
'08 Grand Prix GXP LS4 V8 (Wife's Car)
'09 Pontiac G8 GT 6.0 V8
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 08:03 AM.

 

About Us

The PY Online Forums is the largest online gathering of Pontiac enthusiasts anywhere in the world. Founded in 1991, it was also the first online forum for people to gather and talk about their Pontiacs. Since then, it has become the mecca of Pontiac technical data and knowledge that no other place can surpass.

 

Cold Case Radiators

Cold Case Radiators is a Max Performance company that produces high end aluminum performance radiators at a price point that won't break the bank. Polished and stamped tanks. 2 rows of 1" tubes. Lifetime Warranty.

GTOG8TA.com

GTOG8TA.com is a Max Performance company that manufacturers parts for the 04-06 GTO, 08-09 G8, and 93-02 Firebird/Trans Am platforms.

Copyright © 2017