Low Oil Pressure

[1ntimid8r]

I have a 2010 Silverado, 5.3L, Z71 4x4.  I currently have 189K miles on it, mostly highway miles.  I have always used synthetic oil in the truck, with the FRAM tough guard filter.  I have 40% oil life left on this change.  (About 2500 miles)  It doesn't burn oil or leak.

 

About 1/2 through my oil life cycle, I start getting P0521 codes popping up.  Sometimes the code shows up with 40 PSI, other times it's below 20 PSI.  Oil levels are nominal and within operating range.  I recently changed the oil sending unit and the filter underneath it.  The engine code went away, for a day.  The engine code came back, even though I'm reading around 30-35 PSI.   This morning, the truck started at 40 PSI with the engine light on.  About 15 minutes later, I stopped for gas.  When I started it back up, I had 25 psi and no engine light.

 

This has been a problem in the past and I always attributed it to the oil sending unit.  If I change the oil, it goes away for some time and then comes back.  

 

What is the underlying issue?  Do I have an oil pump issue or maybe the feeder tube has come loose?  Summer vacation is coming and I'm going to be pulling a camper for 2,000 miles and want to diagnose this before we make that trip.

[Mikebtte]

You have 2 oil pressure sensors. The one on the back with a screen is for the dash only. May check the other sensor and make sure it is reading accurately. A mechanical gauge is always nice as well.

[SierraHD17]

Ls engines only have one sending unit and its located at the back of the intake.  There is not a second sending unit.

[mikedeezxxx]

It’s not an LS motor. It’s a Vortec. LS motors have aluminum heads and blocks.

 

 

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[Mikebtte]

14 hours ago, SierraHD17 said:

Ls engines only have one sending unit and its located at the back of the intake.  There is not a second sending unit.

This is correct, way to many TBI engine work for me as of late. Ether way, could still be a bad sensor. Put on a mechanical gauge and check your pressures. 

Second, get a good sensor and don't purchase the cheapest one available.

Standard Ignition 3 Terminal Oil Pressure Switch is not a bad switch. Lift time warranty, Made in the USA and available at O'reilly's 

 

oil Pressure Sensor

[1ntimid8r]

Sending unit and filter screen were replaced with OEM GM parts.  

 

 

[SierraHD17]

1 hour ago, mikedeezxxx said:

It’s not an LS motor. It’s a Vortec. LS motors have aluminum heads and blocks.

 

 

Sent from my iPhone using Tapatalk

 

LS engines is an accepted family nomenclature even from GM.... 

 

Oh and by the way... his LC9 5.3 is an LS by your logic... it has an aluminum block too lol.  

[SierraHD17]

30 minutes ago, 1ntimid8r said:

Sending unit and filter screen were replaced with OEM GM parts.  

 

 

You could check this truck manually but I would actually attempt to check it at the sending units tie in point.  The reason I say this is the accepted method uses a screw on adapter in place of the oil filter which just measures pump discharge pressure.  My own 2013 6.2 shows an 18 psi discrepancy from there and the ecms sending unit..  You have a pressure relief valve downstream of the oil filter plus all the losses throughout the engine.  It's worth checking.. If the engine is good with a mechanical guage it could be a wiring issue or the cluster itself or the new sender.

[Grumpy Bear]

We just did the pressure checks on my motor. Used Snap-On OBDII reader along with a mechanical gauge replacing the filter as in the post above. 4-5 psi difference between the filter and the VLOM pressure sensor port. Yes my motor is not an LS (Ecotec3) and the oil pumps are different but the point is that the dash pressure and the actual pressures differ and substantially. Cluster I would guess but mine was off a pretty even 10 psi so now that I know that I have a credible reference. New filter and pressure sender changed nothing. 

 

Okay all that said. You have a good number of miles on the motor. This low pressure thing is so common on high milers that Melling actually has a pump with 10% more volume for the expressed purpose of restoring pressure those motors. Cheaper than a motor build. 

 

Do the mechanical pressure checks first of course.