Oil pressure problem or faulty sensor? 2000 Chevy S10 4.3L

General Discussion
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I think this is probably a faulty sensor but wanted to see the opinions here. The oil pressure gauge on my 2000 S10 4.3L has started to jump around wildly. The first time I noticed it the pressure was jumping from below normal to above normal, especially when slowing down or accelerating. This initially concerned me but then I noticed it was actually quite erratic.

It would jump around even at consistent engine RPMs and loads. Then at a stoplight I decided to rev the engine and see what it would do. It increased to near the top of the gauge and then I let off. It then dropped to a normal level as the engine idled down, then went to way over max instantaneously, then dropped back to normal and then started bouncing.

The oil is at the full mark, relatively clean to the eye, but nearing the end of my standard 5000 mile change interval. If standing outside the engine bay with the hood open, the engine sounds smooth with no rattles, taps, or knocks.

I do not know about this engine but know some have oil pressure regulators or relief valves that can get stuck. I would doubt this is a problem since I have always changed the oil at between 3000-5000 miles and almost always use synthetic. I has sat around for extended times until recently called back into service so that might be a problem. I had to take care of some problems at first that were almost certainly caused by disuse.

This has been a good truck but it is getting old and I am considering moving it along as I have recently upgraded a couple vehicles by a decade or more in years. I do like the simplicity and ease of repair on my vehicles from the 2000’s era but eventually everything ages out and starts to nickel and dime. I learned my lesson on that and think it might be getting close to letting this one go. The most concerning issue for me is a leaky clutch cylinder that needs to be topped off at least once per week or whenever first driven, whichever comes first. I guess a 2WD isn’t worth much around here so I have heard conflicting values for what it might bring. I have been told of respectable prices from $2500-4000 down to basically scrap, even in running and driving condition. If the latter I will just keep it as a spare until it needs new tires or the clutch cylinder leaks gets worse, then decide.

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Years ago my riviera showed low oil pressure one morning. I swung by the dealer on the way to work. They said it was just the sensor so I drove on and out a new one in that night. Just the sensor. They are cheap so worth a try. They go out all the time. Only other way is putting a mechanical gauge on it. Easier just to replace the sensor and if that isn’t it, time to trade anyway. I’m not a pro.

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I agree with @bing that the sensor is the first place to look. An even cheaper date is to just pull off the wire connector and clean up the contact surfaces, then make sure there is no looseness when you reconnect it.

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If you are looking for the proper thing to do, put a mechanical gauge on it and read the numbers, should be steady at any given RPM and a minimum of around 7-10 psi per 1,000 RPMS, so 14-20 psi @2,000 RPMS 21-30 psi @3,000 RPMS etc etc, check service manual for exact numbers…

With the KOEO you can also ground the single oil pressure gauge wire and the gauge should go to full max, unground the wire and the gauge goes back to minimum, the gauge should be steady and not jump around when grounded…

You can also check the sending unit by checking the resistance (wire removed) to see if it jumps around with the engine RPM’S, it should remain steady at any given RPM and not bounce around… Or bench test it using compressed air…
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If you want the easy way to do it, throw a new sending unit on it and see if it sticks… lol