Intermittent Oil temperature displayed

[GaParker]

2014 Ram 2500 6.4L oil temperature works correctly initially after startup. After a variable amount of time (seconds to minutes) the displayed oil temperature will shoot up and then read -- (dash dash).

Turning off the engine and returning the key to the Run position, or restarting the engine will cause the Oil Temperature to read out correctly for a short time, then revert to --

The voltage on the Oil Temperature sensor is steady and well behaved even when the display goes to --

The voltage on the Oil Temperature sensor is about 0.7 volts when the engine is warm.

The radiator, water pump, heater core and thermostat were recently replaced. The engine was replaced recently (long block) due to MDS failure at 187,000 miles.

The Oil Temperature sensor, ECM and Instrument Cluster have been replaced. The sensor wiring has been replaced.

 

[04fxdwgi]

If it jumps like that , it's either a wiring / voltage problem or the sensor has become heat sensitive and going bad.

Pretty sure they have a solid voltage (5 volts I think) going to them and the return to the PCM is variable part.

Someone else on here that knows more about them than I do will probably chime in.

From the manual:
SENSOR, OIL PRESSURE
DESCRIPTION
DESCRIPTION
The oil pressure sensor uses the following three circuits:
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Signal circuit to the PCM Sensor ground circuit from the PCM 5 volt. Reference circuit from the PCM

The oil pressure sensor returns a voltage signal back to the PCM with. Reference to oil pressure. Ground
for the sensor is supplied by the PCM.

The oil pressure sensor is located on the right side of the engine block. The sensor screws into the
engines main oil gallery.

 

[Dean2]

You say voltage is good and steady, cold or hot. That means you need to replace the temperature sensor. I know you said it is new, so return that one and get another. It sounds defective. You could take the sensor out and test it but putting in a new one is easier. Get an OEM from dealer or Rock Auto, do not order one Amazon.

 

[GaParker]

The Oil Temperature sensor WAS replaced with a NEW OEM Oil Temperature sensor, and behaved the same as the OLD (original OEM) Oil Temperature sensor. It made NO difference.

 

[GaParker]

If it jumps like that , it's either a wiring / voltage problem or the sensor has become heat sensitive and going bad.

Pretty sure they have a solid voltage (5 volts I think) going to them and the return to the PCM is variable part.

Someone else on here that knows more about them than I do will probably chime in.

From the manual:
SENSOR, OIL PRESSURE
DESCRIPTION
DESCRIPTION
The oil pressure sensor uses the following three circuits:
7/18/2019 MITCHELL 1 ARTICLE - 2014 ENGINE 5.7L - (Service Information) - Ram Pickup
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Signal circuit to the PCM Sensor ground circuit from the PCM 5 volt. Reference circuit from the PCM

The oil pressure sensor returns a voltage signal back to the PCM with. Reference to oil pressure. Ground
for the sensor is supplied by the PCM.

The oil pressure sensor is located on the right side of the engine block. The sensor screws into the
engines main oil gallery.

It's the Oil Temperature sensor, which works the same, but the point is it's not the Oil Pressure sensor. Yes, the internal resistance of these kinds of sensors changes with temperature, so the voltage returned to the module changes with temperature. The original OEM sensor did that, as does the NEW OEM sensor. It appeared to function fine, but as someone observed, it is easy to replace, AND in my experience it is the sensors that fail, so I did replace it. The new OEM sensor made no difference.

 

[Dean2]

You had not said the original sensor and the replacement behaved the same way, or at least I did not grasp that when I read your posts the first time. Since both sensors are doing the same thing and you have replaced the sensor wiring, display and pcm, you are going to have to dig deeper into the whole temperature circuit and display. Something is breaking down shortly after power is applied to the circuit. Let us know what you find. Have you tried replacing the actual fuse for that circuit. Rarely do they work intermitemtly but it may also be loose in its slot.

 

[GaParker]

So the voltage on the sensor is absolutely steady when it displays oil temperature and after it fails to display. Which in combination with the replaced OEM Engine Control Module tells me the fuse is not failed.

I guess the next thing to do is look at the sensor voltage with a scope to see if there are glitches the voltmeter is not showing. I know from the products I've designed that we would often 'debounce' an input by sampling and invalidating if we detected a certain number of out of bounds signals. I'm also thinking about looking for grounds on the ECM side of the compartment that might need cleaning. This gets into a sketchy region of ideas, but I'm kind of out of the obvious.

Noise on the power supply can also cause glitchy stuff, but this only happens to Oil Temp, so I don't think that idea holds up. My boss asked me once "Gerry, how does the noise know to take out the same packet on the bus every time?" Yeah. So. I think looking at the signal with a scope is next.

Do you know of a tool that can read the Oil Temperature off the CAN bus? It would be awesome to know if it's still intact on the bus after it stops displaying. That would really tell.

Thanks for the ideas, btw. As much as I drive, I need this to work. Well, need...

 

[Dean2]

Mx+ OBD reader will display oil temp.

 

[04fxdwgi]

^^^^^ 100%. The MX+ also comes with the OBDLink software so you can log and chart multiple PIDs

 

[garycarrick]

I was having the same problem with mine also oil pressure errors on cold starts replaced both. Not had a problem since.

 

[GaParker]

garycarrick Replacede both and not had a problem since... hmm. I'll take a look at that and see what's common between them.​

 

[GaParker]

Today was a busy day and I didn't get a chance to look at it with a scope. I did clean a couple of grounds but the problem reproduced, so no bueno yet.

 

[Dusty]

Today was a busy day and I didn't get a chance to look at it with a scope. I did clean a couple of grounds but the problem reproduced, so no bueno yet.

Are you getting a message in the cluster top check engine oil, or for that matter a check engine indication?

Regards,
Dusty
2019 Ram 1500 Billet Silver Laramie Quad Cab 2WD, 5.7 Hemi, 8HP75, 3.21 axle, 33-gallon fuel tank, 18” wheels. Build Date: 3 June 2018. Now at 151708 miles.

 

[GaParker]

No, no oil related engine messages or any other dtc indications. In the history of this problem, I think I got the High (oil?) Temp dtc error one time, but it didn't repeat.

I drove it a couple of times yesterday and noticed the displayed oil temperature fails when it gets to 235 F. Every time. If it fails and I stop for a minute (engine off) and restart, it will work until it hits 235 F again, then will fail.

This caused me to order Another OEM sensor yesterday, however unlikely it may seem based on what I'm measuring and that I replaced it once already. It also caused me to question if the new sensor I put in was in fact an OEM sensor. Memory is a terrible thing, and it might have been bought at Advanced AP when I was looking for spark plugs...

I'm waiting for the Mx+ OBD reader to arrive so i can see the value on the CAN bus.

But for the money, what is temperature sensitive that fails at exactly 235 F every time? That just sounds like the sensor (or software). So we'll see.

 

[EdGs]

No, no oil related engine messages or any other dtc indications. In the history of this problem, I think I got the High (oil?) Temp dtc error one time, but it didn't repeat.

I drove it a couple of times yesterday and noticed the displayed oil temperature fails when it gets to 235 F. Every time. If it fails and I stop for a minute (engine off) and restart, it will work until it hits 235 F again, then will fail.

This caused me to order Another OEM sensor yesterday, however unlikely it may seem based on what I'm measuring and that I replaced it once already. It also caused me to question if the new sensor I put in was in fact an OEM sensor. Memory is a terrible thing, and it might have been bought at Advanced AP when I was looking for spark plugs...

I'm waiting for the Mx+ OBD reader to arrive so i can see the value on the CAN bus.

But for the money, what is temperature sensitive that fails at exactly 235 F every time? That just sounds like the sensor (or software). So we'll see.

Is your coolant temp anywhere near the 235° you're getting for the oil temp?

Not sure with the 6.4, but in my '15 SLT 5.7 the oil and coolant temp sensors are the same.

I recently bought an OE temp sensor for my 5.7 (part #5149077AB, verify your specific part #s for your 6.4, though). Was only $68, so not too bad.

Do not but OE from Amazon or Ebay, polluted with counterfeit parts. Buy at dealer or OE part # through RockAuto. I went dealer because was only ~$15 more than Rock, and did not have to ship and wait.

Keep us posted.

 

[GaParker]

I recently rebuilt the cooling system. Replaced the radiator, water pump and thermostat assy due to overheating when towing. Also replaced the associated hoses. Anyway, the coolant runs anywhere between 206 F and 219 F when the oil temp hits 235 F.

Yes, I bought the newest sensor from an online dealership where I bought the coolant stuff, and that looks like the same PN I ordered (I remember the 49077AB).

Agreed, counterfeit parts are prolific in many industries. In the research i did yesterday, I see 'companies' selling these sensors with a top end temp rating of 230 F. The OEM part says an upper end of 259 F. That's when I ordered the new part...

It used to be useful to type Part Number + 'specifications' and you could get a data sheet in the first page or two, but that's not working so well now.

With the integrated thermostat + housing it's not clear it's the same sensor (this one has a right angle connector and doesn't seem removable). But you can guess the 230 F part might be (almost always) fine for the coolant, but not for the oil. Although I think the coolant overheat DTC hits at 251 F, so in an overheat situation, that sensor would fail before the DTC set.

 

[EdGs]

Have you tried an IR temp gun at the points where the sensors are attached?

How hot does your transmission run?

Very strange that your oil temp is high like that. I have no idea the differences between your 6.4 and a 5.7. In my 5.7 the high coolant temp. triggers at 240°, I believe.

I hit that 240° when my radiator shat the bed. Scared the shat outta me, too. I do not like those 215°+ temps, and use a 192° stat now.

 

[GaParker]

Before flushing, and then replacing the old radiator, I saw coolant temps at and above 219 F just the truck itself. If I towed anything it just went up from there.

Before all this started, I was seeing 217 F or 218F oil temperature typically, even when the coolant was spiking.

Dealership put Pennzoil in last time they had it (I don't know what weight), I had been running Mobil 1 full synthetic 0W-40, so I don't know if the oil temp is because of the replaced (questionable) sensor, or the dealership oil.

There's a bulletin somewhere that says to run 5W-40 oil to try to reduce the lifter damage due to low oil pressure at idle. I tried 5W-40 and noticed the oil temp definitely went up about 10 F, maybe 15 F (I went back immediately to the 0W-40). I don't know what weight the dealership put in. I'll have to take the oil filter off to put in the new sensor, so I'll replace with the 0W-40, so still won't know because I'll be changing two things at one time...

In a related note about oil temperature, I put an oil temp sensor on a diesel engine I rebuilt right at the crank galley output (there was already a plug there with the right size and thread). The oil temp coming out of that galley was 100 F higher than the coolant temperature, and about that much higher that the oil pan oil temperature.

I consulted with my GM guy, and he correctly guessed the oil temperature at the galley before I told him. He worked closely with the GM service departments and occasionally consulted with their designers. Said that was absolutely normal, and one of the reasons oil takes such a beating, because it gets so hot in those main bearings. So when you say "high" oil temperature, I think that's very dependent on where it's measured.

 

[Wild one]

Before flushing, and then replacing the old radiator, I saw coolant temps at and above 219 F just the truck itself. If I towed anything it just went up from there.

Before all this started, I was seeing 217 F or 218F oil temperature typically, even when the coolant was spiking.

Dealership put Pennzoil in last time they had it (I don't know what weight), I had been running Mobil 1 full synthetic 0W-40, so I don't know if the oil temp is because of the replaced (questionable) sensor, or the dealership oil.

There's a bulletin somewhere that says to run 5W-40 oil to try to reduce the lifter damage due to low oil pressure at idle. I tried 5W-40 and noticed the oil temp definitely went up about 10 F, maybe 15 F (I went back immediately to the 0W-40). I don't know what weight the dealership put in. I'll have to take the oil filter off to put in the new sensor, so I'll replace with the 0W-40, so still won't know because I'll be changing two things at one time...

In a related note about oil temperature, I put an oil temp sensor on a diesel engine I rebuilt right at the crank galley output (there was already a plug there with the right size and thread). The oil temp coming out of that galley was 100 F higher than the coolant temperature, and about that much higher that the oil pan oil temperature.

I consulted with my GM guy, and he correctly guessed the oil temperature at the galley before I told him. He worked closely with the GM service departments and occasionally consulted with their designers. Said that was absolutely normal, and one of the reasons oil takes such a beating, because it gets so hot in those main bearings. So when you say "high" oil temperature, I think that's very dependent on where it's measured.

Your 6.4 also has piston oil squirters which contribute to the 6.4's running hotter oil temps then the 5.7's do.I found 5W-30 Redline to be one of the better oils to run in my wifes 1320 Challenger with the 6.4.It liked it alot better then 0W-40 PUP with a bottle of Lubegard.It was alot quieter in regards to lifter noise. 5W-30 Redline is thicker at operating temps then alot of the 0W-40 oils,and doesn't break down/shear as much as the majority of 0W-40 oils do.

 

[EdGs]

I wonder if your water pump is causing an issue like the impeller spinning on the shaft, etc. Very rare, but possible.

Really hard to say without verifying coolant temps at the point of measurement.

But I'm talking coolant temps too. Your issue is oil temp. Sorry about that.