First Post-Oil Pressure Issue

[Diesel Thunder]

Hello All,



As stated in the title, this is my first post on the TDR. I have been following the threads for years, and finally joined within the last year. This site is an amazing resource.



My question concerns the factory oil pressure guage, I understand that it is controlled via ECM input and not by an actual sending unit and is based off of a 6 PSI switch. That aside, last night I changed my oil (5K interval) with the Mopar Oil Filter and 12 QT 15W-40 Mopar Oil. Well, upon restart and an easy drive to reach operating temps, I decided to "get on it. " After my smoke screen, my factory oil pressure guage reads lower than ever--at idle the needle sits right at the lower green mark of the "safe zone. " I have owned the truck since new and now have 25K on it. Previously, the needle never reached the lower green mark at idle--regardless of the temp (both outside environment and coolant). I am wondering if I need to visit the dealer? There are no leaks, and the dipstick reads FULL. If the gauge does not sense actual pressure, then what would cause a change in the "programmed sweep" of the needle?



I read on another post about a Bypass valve in the oil filter/oil filter housing? If this valve exists, is it possible that during my hard acceleration that the oil pressure spiked and caused the valve to stick--possibly open?



Thanks in advance for your input.

 

[Diesel Thunder]

P. S.



My truck profile did not show. It is a 2005 2500. Stock, Boost/EGT Gauges, NV5600.



Thanks...

 

[JApol]

Put your truck info in your signature, then it will show

 

[steved]

Hello All,



As stated in the title, this is my first post on the TDR. I have been following the threads for years, and finally joined within the last year. This site is an amazing resource.



My question concerns the factory oil pressure guage, I understand that it is controlled via ECM input and not by an actual sending unit and is based off of a 6 PSI switch. That aside, last night I changed my oil (5K interval) with the Mopar Oil Filter and 12 QT 15W-40 Mopar Oil. Well, upon restart and an easy drive to reach operating temps, I decided to "get on it. " After my smoke screen, my factory oil pressure guage reads lower than ever--at idle the needle sits right at the lower green mark of the "safe zone. " I have owned the truck since new and now have 25K on it. Previously, the needle never reached the lower green mark at idle--regardless of the temp (both outside environment and coolant). I am wondering if I need to visit the dealer? There are no leaks, and the dipstick reads FULL. If the gauge does not sense actual pressure, then what would cause a change in the "programmed sweep" of the needle?



I read on another post about a Bypass valve in the oil filter/oil filter housing? If this valve exists, is it possible that during my hard acceleration that the oil pressure spiked and caused the valve to stick--possibly open?



Thanks in advance for your input.

Even if the bypass valve stuck open, the guage reading would not reflect it.



Your guage should not change, unless dictated by the ECM, which HAS NO DIRECT READING of oil pressure other than less/greater than 6psi.



Get a real guage and read your oil pressure... it will look nothing like the dash OEM guage.



steved

 

[Badunit]

As you said, the "gauge" is really just a switch. So there is no relationship between the actual oil pressure and the gauge reading, as long as it's above 6 psi. I would imagine that the gauge reading is based on engine rpm, coolant temp, and maybe a few other things. If it was really sophisticated it could factor in throttle position over a period of time and the result that would have on oil temperature and viscosity. I doubt it's that smart but who knows. Could be just a hot day and the coolant temp or outside air temp was higher than usual, resulting in a low oil pressure display.



You could try the diagnostic test of the instrument panel and see if that gauge is acting correctly. With the ignition off, hold down the trip/odo button and, with the button held down, turn the switch to on but don't start the engine, then let go of the button. Your panel lights should light up and the gauges should sweep. The gauges should go to several "calibration" points during their sweep. At the end the display should display "c code" followed by two pairs of zeros. Or. if there was a fault, it'll display a code for that.

 

[HGreen]

If its really true, could you add a real sending unit and get real oil pressure readings? Why I ask, is that I also have a Miata, and they have a real gauge, but the sending unit is just one on the on/off switches. Many of us have added a real sending unit (I got one from eguage.com) and replaced the factory unit. Had to reset the needle, but now I see the a change going from idle to redline and back. If the ECM used just the on/off signal, there could be a problem with warning lights, etc. I guess. Any thoughts?

 

[Badunit]

On our engines, the signal goes though the computer so replacing the sending unit probably isn't the answer. The computer will continue to compute the "oil pressure" to "meet customer expectations". Personally, this customer's expectation is that a gauge should be measuring something for real, not faking it.

 

[rbattelle]

Great advice on this thread. As everyone points out, there's no point in looking at the factory gauge because it isn't real. You've got to hook up an aftermarket gauge to the top of the oil pressure port. I'd bet your oil pressure is fine and, as Badunit points out, the recent hot weather has the factory gauge reading a little lower than usual. Couple that with your psychological belief that "something's different", and whammo! Instant oil pressure problem!



As far as what I've read on these boards over the years, the oil system on the ISB is exceptionally reliable. It's very rare for anything to malfunction (which is probably one reason Dodge decided to give us a fake gauge).



HGreen - interesting idea about installing a real sender, but I agree with Badunit that it won't work with the ECM.



Ryan

 

[6speed]

Badunit you said you can do a diagonisic check on the instument panel. The guages should go thru several calibration points. The you mentioned at the end the display it should show a "C Code with 2 pairs of zeros. Where well this display appear. Will it appear on the odometer. Just curios as I have installed a REAL gauge in mine. It shows about 25 lbs at idle and about 65 at highway speeds. Oil temp is about 180.

 

[Badunit]

It appears on the odometer.

 

[Diesel Thunder]

Thanks all,



I will look into getting a true oil pressure gauge. I currently have the Isspro EV white face, red pointer gauges on the pillar. However, has anyone found the same style--only in the oil pressure setup? I have been unable to locate it. I hate the fact that Dodge has given us a fake gauge. Thanks again for your thoughts.



-Diesel Thunder-