How do you know if the oil pressure gauge is bad?

...if you are really interested in the oil pressure, install a mechanical pressure gauge...sometimes I believe these electronic goodies cannot be trusted...I'd look for a bad ground givin' an unreliable signal to the sensor~

Did you check the oil level in the engine? Make sure the vehicle is on level ground and shut off for at least 10 minutes to allow all the oil to drain into the pan. Pull out the dip stick, lean it off and re-check the oil level on the stick. I always do this twice to make sure. It may be that simple of a fix. It may be the sensor sender, the gauge, or faulty or lose wiring.

I'm with judge_roy on this. What you see on the dash is an INDICATOR - an idiot light with a needle. The only way to know is with a mechanical gauge.

Some answers on other posts about low oil pressure readings suggest pulling the oil sensor and remove the screen that sometimes gets gunked up. Where do you live? Do you have winter grade oil in your motor and are now driving in triple digit heat? Sometime 5W-30 is fine for cold weather, but 10W-30 or even straight 30 weight is better for hot climates. When does your 1500 show low pressure? In town driving with our without a load? Highway pulling a load or empty? How many miles do you have and is it a work truck what has been worked hard? If it is always showing low pressure, go to a good mechanic to hook up a mechanical gauge to eliminate or show it is your current gauge causing the problem. Everyone here is trying to save you money and an overhaul.

@ califcarson: No offense intended but the advice you gave about motor oil viscosity is about 30 years old. The best way to wipe out a motor QUICKLY is to put the wrong oil in it. Engines today are designed with clearances that will cause bearing killing cavitation is the oil's too thick or not lube or cool anything if it's too thin. Follow the manufacturer's recommended type and viscosity - unless you prefer walking.

Tracy, than why does the dealer give me the option? Or do they want me to "walk" or buy a new motor or get a new car? And my car is 44 years old. I ran Valvoline 50 weight oil in it for over 30+ years with no problems with the oil or engine temp except when the water pump went out or the timing chain let go. So your telling me a 10W30 oil must be run in a engine to properly lube and cool it rather that a straight 30 weight in a hot climate? I like what some of the new engines do, but am equally unimpressed with the replacement of metal parts for plastic, or gaskets that will not seal like in the GM v-6s or rear main seals. But this does not answer the question here does it?

I did a little research on you cavitation theory. Here is the summery of an extensive study conducted by exon. ( I think this test verifies my earlier comments that most daily driver engines can use any oil from a high quality 5W20 to a 15W40 fleet oil.] Summary: It was found that HTHS correlates better with wear values found in actual oil analysis and actual tear-down measurements than does measuring the oil film thickness in situations.) The study found the pumping system needs to handle the oil to maintain correct pressure. The oil also needs to be at a high temp. to lubricate properly and most civilian car engines can operate on 5W-30 to 40 weight without any issues.

...as long as there IS some oil, really matters not what~ a dry scrape is never preferred~

I'm telling you (and others) to use the oil specified for the engine or you run the risk of wearing it out prematurely. Just because an ancient piece of machinery works ok with whatever you put in it doesn't mean that today's engines will do the same. BTW - the only thing a dealer is interested in is profits - they don't give a #$% about your engine and usually, don't even know what the "w" in 5w/20 stands for let alone why to use it. Lots of luck with the "ANY" oil theory. It doesn't work in the real world.

...or runnin' it for ever without ever looking and do not even know what oil is...then needs to be educated after the 20,000 oil has broken down to where is but a wee wisp of elastic...yeah...seen them this way too~ oil changes are needed if'n the things gonna last a hoot~

califcarson, cavitation is used to clean jewelry and we had a tank (stolen from a submarine) at the instrument repair place we used to dunk the trumpets into to remove all traces of varnish...yes carson---is a useful tool, but not when the pistons are cavitatin'~

You get used to minor Quakes, just had one in this California location where there are man-made earthquakes as steam is extracted to generate power in a sort of "fracking" for the hot-stuff, quakes are a sad by-product...hey, this is California...get used to it~

calpine.com

Funny that there are as many studies done and none support weather it is wise to stick to a strict oil viscosity or not to be so anal. Yes the new oils are made different than those 40 years ago, and the material used in today's motors are different as are the computerized assembly of these engines vs. hand build. The one study I noticed was the oil was tested on marine engines and diesel engines that have a hard load most constantly. The study found the operating temperature is more important for the preventing of destructive cavitation than the weight of the oil within reason. Rear end grease will not work, but 10W-30 or even 40 weight was insignificant in this study on the bearing wear of everyday motorized vehicles use on the roadways. The different viscosity gave off different reading of wear under sustained heavy loads. BYW, I no longer use 50 weight racing oil in my Vette, and use factory recommended 10W-30 in my Buick and Pontiac. The oiling of the bearings are better starting at a lower weight when cold on these newer engines. What I originally said was to check the oil and if the incorrect oil was in the motor, to correct it.

When I was learning to drive when gas was 29 cents a gallon, it was understood any car or truck started should not be driven until the engine temp came up to near operating temperature so a bearing would not be spun due to lack of lubrication under normal loads. I'm sure it is the same now, but perhaps with the 5W-30 or 10W-30 oil recommendations, it is not as crucial to weight for a warm up. I still cringe when I see people start their cars cold, and floor it to take off. That engine will have cavitation issues no matter what the oil they have in the motor. Cold oil will cause the air gas bubbles or other oil bubbles in the bearings and create excessive wear if the oil is not up to proper operating temp before forced loads are applied. Good lesson for the day. Slight edge to you, but I'll not consed it all.

Both my 50&51 Chevy pickups had the 216 with spash oiler (no oil pump)...it wasn't too many miles before people replaced them with the 235 with an oil pump...so "spash" oil system is a bust...they both had a hand crank start and a hole in the floor that the foot pedal applied the motor to the starter (human body as the solenoid)...there is something graceful about these...never could afford the restoration...off to the scrapper...sadly~

Yes Roy, back then a engine with 25,000 miles on it was ready for a rebuild, 0.010 bore, new rings and the crank was turned 0.010 also. At 50,000 miles a new motor may have been in order if it even got that far. Oh the good old days. No worry if you had 5 or 10 weight oil, just good old 30 and go.

...buddy. am glad that someone carries some authority with these~ While I owned them, someone had disposed of a toxic substance in the gas tank...could not get either engine to turn over....even after removin' the heads~ loved the little flapper in the center of the outside to let air in, but the tiny cab (despite enormous engine cavity) and floors that would spill out to the doors if you spilled a beverage...at an aggressive angle made it unfriendly to sit in...even~....good riddance...chevy trucks do die...I assert~

The interior floors were built that way so the farmers could just throw a bucket of water inside to flush out the crap "literately" and mud. Simple wires and switches. 5 miles to town was as far as you were suppose to go. They did haul a lot in the weight category,, and had very low gears. I remember some farmers in Iowa using them to pull the plow when the farm tractor was down for repairs.

Since last three months, I was facing oil pressure problem in my Chevy Suburban 2004 over 200,000 MI, the oil pressure needle was unstable and some time stuck at Zero with low oil pressure massage and warning sound, although engine was running stable without check engine light, I went to mechanic, he changed the oil sensor, cost me 50$ without solving the problem. Now he is saying it is a bad stepper motor of the oil gauge or bad electrical wiring. I asked him to remove the oil sensor wire which has resulted in zero oil pressure on the gauge with no ding dong disturbing low oil pressure message or check engine light. In my opinion, better way to test the bad oil sensor in GM vehicles is just remove the sensor wire and switch the ignition at on without starting the motor, if oil pressure gauge move to full at 80 in that case you have a bad oil pressure sending sensor and unfortunately, this test was not performed by my stupid mechanic before changing the good oil sensor.

For vehicles with an oil pressure gauge, the sending unit (located next to the oil filter) is essentially a variable path to ground for the gauge. When the engine is off, the sender is shorted to ground, and the gauge reads "0" psi (or close), as the oil pressure increases, the sender offers resistance to ground, providing a mid scale readings on the gauge. If the wire is removed altogether, the gauge will read off the scale to the high side (3:00 position) all the time. This is a quick and simple test you can perform to help isolate the problem. With the key ON - engine OFF, pull the wire off the sending unit. The gauge should read full scale. Now short the wire to ground (this will not harm anything), and it should read "0". If this is correct, then your gauge, and the wiring is good, and your trouble is likely to be the sending unit. If this test has little or no effect on the gauge, then your problem is in the wiring or the gauge itself.