Help PLEASE. Engine off, high oil pressure.

[Josh22855]

You can unplug the pcm connector, turn the key on and it still shows oil pressure on the instrument cluster. #4 terminal on pcm has 5 volts on it with the key on and pcm connector unplugged.

I have already changed out the PCM, replaced oil pressure sensor, wiring checked out good.

This problem happened Immediately after I pulled the engine from a 2017 ram 1500 (5.7) and replaced it with a 2016 ram 1500 5.7.

So my CEL will stay on now, when the engine is on or off the pressure will remain the same. (Always showing over 92psi)

Any help or recommendations are appreciated.

 

[Danes]

This will sound weird, but have you unplugged the oil PSI sensor and measured resistance across it? If it’s “open” this could point to your problem. Not sure what that measurement should be, but if it’s not than 1k ohms it’s definitely not a good sensor


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[Josh22855]

Sensor has been ruled out.
Tried multiple sensors.
Vehicle displays high oil pressure with wiring harness completely unplugged from pcm.

 

[Danes]

That’s interesting.....is there a broken wire leading into the harness?


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[Ashkon]

This is for my 18 ram but should be the same as yours. Looks like you should have a 5 volt supply at the ecm. That’s the feeding voltage.

 

[Ashkon]

Sorry here’s the picture

 

[62Blazer]

Hmmm, I wonder if they revised the wiring or made a change in the ECM software between the years? I don't know this for sure on this particular truck but on some models, including some older Rams I've work on, the oil pressure sender is just a on/off switch.........you have oil pressure or you don't. The gauge really isn't any different than having a dummy light on the dash. Basically what happens the ECM senses you have oil pressure than calculates what it "should" be based on some parameters like RPM, temperature, etc.... We had a brand new 3500 Cummins at my previous job that when you first started it the oil pressure "gauge" went up to normal and no warning lights could come on, and you would take off driving. About 30 seconds later the gauge would drop to zero and the warning lights would come on. Since the it showed oil pressure at start up we thought it was a simple bad wire or something and started it up a couple times trying to diagnose it, then it suddenly started knocking. Removal of the oil pan found the oil pickup tube had fallen off so obviously it was never getting any oil pressure. Point being the ECM was showing oil pressure at startup and only saying there was no pressure after it ran through the full diagnosis cycle after start up.

 

[Josh22855]

Yeah my mechanic is stumped on this issue, everything is checking out fine besides the pressure displayed on the instrument cluster. I am not sure what to do from here.

 

[62Blazer]

Check the signal from the ECM to the gauge.

 

[Daw14]

Add a mechanical gauge.

 

[Hemi395]

What does the PCM show as oil pressure? That will at least tell you if the data is wrong getting to the PCM or from the PCM to the cluster....

Also are you using an OEM sensor?

 

[Josh22855]

What does the PCM show as oil pressure? That will at least tell you if the data is wrong getting to the PCM or from the PCM to the cluster....

Also are you using an OEM sensor?

Yes, OEM sensor. Tried 2x OEM sensors and had same outcome with both.
For example I'll turn truck on and oil pressure will show 92 psi and remain that same pressure until the next time I turn ignition to the run position or start engine, then the pressure will be a different value (always 92 psi or above) and remain the same value throughout the duration of engine running/key in the run position. I am not understanding why there is even a numerical value on the instrument cluster when the connections are completely removed from PCM.

 

[indept]

Hmmm, I wonder if they revised the wiring or made a change in the ECM software between the years? I don't know this for sure on this particular truck but on some models, including some older Rams I've work on, the oil pressure sender is just a on/off switch.........you have oil pressure or you don't. The gauge really isn't any different than having a dummy light on the dash. Basically what happens the ECM senses you have oil pressure than calculates what it "should" be based on some parameters like RPM, temperature, etc.... We had a brand new 3500 Cummins at my previous job that when you first started it the oil pressure "gauge" went up to normal and no warning lights could come on, and you would take off driving. About 30 seconds later the gauge would drop to zero and the warning lights would come on. Since the it showed oil pressure at start up we thought it was a simple bad wire or something and started it up a couple times trying to diagnose it, then it suddenly started knocking. Removal of the oil pan found the oil pickup tube had fallen off so obviously it was never getting any oil pressure. Point being the ECM was showing oil pressure at startup and only saying there was no pressure after it ran through the full diagnosis cycle after start up.

Wrong answer, the sensors for a guage outputs a variable voltage based on pressure. The sensor for idiot light is on or off.

 

[62Blazer]

Wrong answer, the sensors for a guage outputs a variable voltage based on pressure. The sensor for idiot light is on or off.

As I explained, not always. Go look up that part and most places will list it as an oil pressure "switch" and not a "sensor" which implies it's on or off. I I also specified that for this particular vehicle I don't know for 100% sure, but you can verify by logging the output voltage from this "sensor" and see if you actually get a variable voltage output or just a zero or 5 volt number. The factory service manual should also provide this manual. For my example stated where we had a truck with this condition it was while performing powertrain durability testing directly for the company, at the time still DaimlerChrysler, and we were working with their engineers and Cummins directly.

 

[crackerjack1957]

I would confirm with mechanical gauge.......if normal then its got 2 be electrical.

 

[indept]

As I explained, not always. Go look up that part and most places will list it as an oil pressure "switch" and not a "sensor" which implies it's on or off. I I also specified that for this particular vehicle I don't know for 100% sure, but you can verify by logging the output voltage from this "sensor" and see if you actually get a variable voltage output or just a zero or 5 volt number. The factory service manual should also provide this manual. For my example stated where we had a truck with this condition it was while performing powertrain durability testing directly for the company, at the time still DaimlerChrysler, and we were working with their engineers and Cummins directly.

The reason it's sometimes called a switch is thr person that enters that description isn't necessarily a technical person so they enter what they're familiar with. Quite often it's listed as an oil sender switch, that doesn't mean its off or on only. That description is the same as calling all brands of facial tissue kleenex. Your description of an algorithm that gives a pressure calculated fron the engine rpm is totally wrong. That sensor has been used for many decades. Before computerized control that variable voltage signal would go directly to an analog meter on the dash, the higher the voltage the more the oil pressure meter deflected a lower voltage meant lower pressure.

 

[Murdered Ram]

Im having the same issues on my ram I have a 3.6 pentastar 2015 mine gets stuck on 98 psi or 99 psi I changed the switch already and even replaced my whole filter housing which came with a brand new one as well so basically I changed it out twice and still stuck at 99 psi

 

[lpennock]

The reason it's sometimes called a switch is thr person that enters that description isn't necessarily a technical person so they enter what they're familiar with. Quite often it's listed as an oil sender switch, that doesn't mean its off or on only. That description is the same as calling all brands of facial tissue kleenex. Your description of an algorithm that gives a pressure calculated fron the engine rpm is totally wrong. That sensor has been used for many decades. Before computerized control that variable voltage signal would go directly to an analog meter on the dash, the higher the voltage the more the oil pressure meter deflected a lower voltage meant lower pressure.

Ram uses both methods. Cummins is just a pressure switch and the computer calculates a pressure to display. Other engines have an actual sensor. I think the Eco Diesel is one. Not sure on the 5.7 but base on the connector diagram posted earlier I would believe it to be a sensor.

 

[lpennock]

Yes, OEM sensor. Tried 2x OEM sensors and had same outcome with both.
For example I'll turn truck on and oil pressure will show 92 psi and remain that same pressure until the next time I turn ignition to the run position or start engine, then the pressure will be a different value (always 92 psi or above) and remain the same value throughout the duration of engine running/key in the run position. I am not understanding why there is even a numerical value on the instrument cluster when the connections are completely removed from PCM.

Sounds like you may have a short in the harness. When the senor line is about 4.5 V that would tell the computer to go to max output. About 0.5v is 0 psi.

Try disconnecting both ends and check for a short (or low resistance) between the 5V and the sense line.

 

[RedSRT4Me]

Who was the guy who said removing his oil filter fixed his pressure issue?

You might have that much pressure built up and no way of relieving it.

Get the tools out, drop the oil pan and get to work