My Chevy 2500HD 6.0 liter has developed a problem. My oil pressure has always been 40 psi at idle and 50-55 psi on the freeway. Yesterday it started idling at 30-35 psi and 50-55 psi on the freeway.I know it is within specs, but why did it change overnight ? The other thing I noticed is that the gauge responds slower than it used to and on the freeway it can be erratic at times. It will jump back and forth between 50 and 55 psi and sometimes it does the same thing between 30 and 35 psi at idle. The instrument cluster has the updated stepper motors as well, but I am wondering if the sending unit could cause this or if it is something mechanical. Why would it happen overnight ? I also changed the oil and filter with a new AC Delco filter and Mobil One 5w30 oil. Any input would be appreciated.

Gage going bad, nothing wrong with the engine?

There’s also an oring that is in the oil pump that goes bad as well. YouTube has a few vids on that. I hope it’s not that because it’s a bear to get to. How many miles on the truck? I’m thinking sending unit or weather changes possibly, or a grounding issue ?

I'm with DutchmenSport, stepper motor going out in the cluster.

Have you tried testing oil pressure from the ODB2 connector? That might tell you if the sensor is bad. I’m also told that when the gauge starts acting up, turn off the engine and restart immediately-if the gauge reads normally you have a stepper problem.Hope that helps.

Stepper motors have were replaced last year. No issues with the truck at all and it does have 206,000 miles. I read about the O-ring, but it seems I have different symptoms. I may spend the 60.00 and replace the sending unit and see what happens. I just find it odd that it happened overnight and the O-ring thing scares me a little. I have the ability to fix it, but I really hope I don't have to do it because my wife hates it when every other word out of my mouth is a swear word.

03 Silverado oil pressure | Good Sam Community

DutchmenSport
Explorer
Dec 07, 2017
Gage going bad, nothing wrong with the engine?
kw_00
Explorer
Dec 07, 2017
There’s also an oring that is in the oil pump that goes bad as well. YouTube has a few vids on that. I hope it’s not that because it’s a bear to get to. How many miles on the truck? I’m thinking sending unit or weather changes possibly, or a grounding issue ?
jaycocamprs
Explorer
Dec 07, 2017
I'm with DutchmenSport, stepper motor going out in the cluster.
TakingThe5th
Explorer
Dec 07, 2017
Have you tried testing oil pressure from the ODB2 connector? That might tell you if the sensor is bad.

I’m also told that when the gauge starts acting up, turn off the engine and restart immediately-if the gauge reads normally you have a stepper problem.

Hope that helps.
Thunderbolt
Explorer
Dec 07, 2017
Stepper motors have were replaced last year. No issues with the truck at all and it does have 206,000 miles. I read about the O-ring, but it seems I have different symptoms. I may spend the 60.00 and replace the sending unit and see what happens. I just find it odd that it happened overnight and the O-ring thing scares me a little. I have the ability to fix it, but I really hope I don't have to do it because my wife hates it when every other word out of my mouth is a swear word.
enblethen
Nomad
Dec 08, 2017
I would be looking at the sending unit. Many GM products use the sending unit as a switch for the fuel pump. Look for leak on sending unit.
NMDriver
Explorer
Dec 08, 2017
I do not claim to be an expert but what was the oil before you changed it? I have been told that a switch from fossil oil to synthetic will cause a oil pressure change. I cannot say if it is true or not since I have always used synthetic oil with the API CJ-4 and CI-4 Plus rating.
LIKE2BUILD
Explorer
Dec 08, 2017
Thunderbolt wrote:
Stepper motors have were replaced last year. No issues with the truck at all and it does have 206,000 miles. I read about the O-ring, but it seems I have different symptoms. I may spend the 60.00 and replace the sending unit and see what happens.

Even repaired stepper motors can go bad. But, I agree, I'd put an ODBII reader on it and see what values are being reported.

One priceless thing I've found is an ELM327 ODBII Code Reader and then I installed the DashCommand App on my phone. This is really handy because any time there is a CEL you can check and clear codes but you can also look at PID's like oil pressure in live time and see what's really happening.

If the pressure is out of whack and the gauge is in-line with what the app says, then you could look at the sending unit. If a new sending unit doesn't change anything then you might look at the oil pump o-ring issue.

KJ
FlatBroke
Explorer II
Dec 08, 2017
My 03 dmax showed “low”pressure since it was new, put in a new sending unit a couple of years ago and pressure shows considerably higher now.
bucky
Explorer II
Dec 08, 2017
The 4.8, 5.3, and 6.0 gassers of that vintage are known for blocked oil passages to the lifters at high mileages. Are you hearing any valve train noise at idle that goes away at higher RPMS? Seafoam and Marvel Mystery oil can help if so. Lots of vids on Youtube about it.

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