still can't get oil pressure reading
 

I have been having trouble getting my 3 wire oil pressure signal to report correctly in HPTuners. I've switched the wires around with no luck, it either pegs out the reading on something like 130 or -15 depending on which way the wires are connected.

I'm going to try a new OP sensor tomorrow and see if that works.

411 PCM with the wiring done appropriately. Any ideas?????

128 views and nothing?

Nothing because no one knows WTF you are working on.

Sometimes I don't even know what I'm working on :jest:

Vehicle is a 90 Chevy truck with a bunch of other parts in it that didn't originally come that way.


It's a 2003ish LQ4 with a 411 PCM, oil pressure wired up as a 2000 vette PCM would be for the oil pressure sensor.

I'm right in your backyard, Guthrie OK

What OS in in the PCM?

I gave him the idea because I did it to mine.
I'm running a 99 Camaro OS.

It's a 411 PCM running a 3 bar SD operating system. I'm using layout files that Ron gave me.

Here's a short log of the oil pressure sensor readings with me switching wires around seeing if maybe I had some backwards, nothing seems to make sense so I'm wondering more and more if the sensor itself is bad.

Also figured I'd ask. What are you guys doing to feed oil pressure to your dash gauge?? Does that require another sending unit yet? That's the only gauge on my dash I haven't figured out.

I'd like to get oil pressure on my dash gauge as well as in Hptuners.

-----EDIT-----

I'm really confused about this LS style 3 wire pressure sensor. If I'm understanding this correctly, this is a SENSOR and not a SENDING UNIT like I'm used to dealing with.....
So I take this to mean that there is ABSOLUTELY NO WAY this sensor will give a signal to the PCM and ALSO give a signal to my original dash gauge? Do I have this right???

Don't know what a layout file is. That is not a PCM term. What is the year and vehicle type in the PCM?

The term layout is what I got from Ron, as in the layout for the gauges and sensor inputs in the scanner portion of the HPtuners software suite I guess. The obd2 world is still a learning experience for me at this point.

The pcm says 02 v8 f body when connected to it in the scanner

What application OP sending unit are you using? What PCM pins are you wiring it to? I don't understand how you are trying to make it work with a 02 F-body OS. A 0411 with a 02 F-body OS has no pins assigned for OP sending unit input and uses a 2 wire sending unit with ground and output going directly to the cluster. A 02 Vette uses a 3 wire OP sending unit and is wired to the PCM. Those pins are either not used or reassigned to a different function with a F-body OS.

Well....

You're not entirely wrong! The pins are labeled (Not Used) on every schematic I've seen for the FBody PCM at those pin locations. But whether it was used or not, the capability to use the input signal is still there.

Turns out all I needed to do was purchase a new sensor. See attached log showing oil pressure functioning.

Just to confirm...... A 411 PCM from a 2002 F body WILL report oil pressure to the datastream. Just have to configure it as a PID, wire it up to the PCM and most importantly USE A GOOD SENSOR!!!

My understanding is this. While not all 411 PCMs were factory equipped to have oil pressure as in input in the datastream, ALL or nearly all of them will accept it.


I am using a 2003-ISH stock truck oil pressure sensor (3 wire)... The Corvette sensor APPEARS to be the same P/N#. It is wired like a 2000 Corvette. Harness is a RED AND GREEN harness that I converted to a RED AND BLUE....

I bought a new sensor today to rule that out. The new sensor fixed it!

Wire the 3 wire oil pressure sensor to the 411 F body PCM like a 2000 C5 Vette and use a 3 wire sensor for either the Vette or a 2003-ISH truck.

IF you are converting a RED/GREEN harness to RED/BLUE like I did, then among other things, you will have to pin in a TPS for the conversion from DBW to DBC.

BOTH the TPS and OPS get their 5V REF from either pin 7 OR pin 8 BLUE. BOTH the TPS and OPS get their LOW REF from pin 60 OR pin 63 BLUE. It does NOT matter which pin is used at THE PCM. Just as long as the 5V REF and LOW REF are wired correctly on the corresponding sensor.

I can't really rely on any one application specific solution as my build is all over the place.... S475, stock LQ4(LS9 gasketed and ARP bolted)'90 chevy truck, LT1 T56 converted to LSx, LS7 clutch, custom aluminum DS, 454ss rear 4.88s&TruTrac diff, 4 wheel discs, Jeep steering shaft, 454SS box, 02 411 F body PCM(running 3 BAR SD OS), RED/GRN harness converted to RED/BLU,, ZR1 MAP, Walbro 450, decapped injectors, lots of braided stainless........I'm using PEX elbows to give me the 90* kick I needed to route my heater hoses up from the water pump and AWAY from my 5" downpipe and hotside. Solid motor mounts and poly everywhere else. etc.

Ron I've got to tip my hat to you yet again for helping me figure this out. Much appreciated.

:cheers:

The pins were open in my 99 Fbody harness so I added them connected to a 3 pin pressure sensor.
it works fine.
I realize that the Fbody simply had a dash mounted oil pressure gauge and was not read by the pcm.
But I also have a Corvette, same pcm so that's how I decided to give this a try.

It's a bit unique in that the pcm in the Vette assumes a 0-130 psi sensor. Most common sensors are 0-100 psi. But some simple math gets it to display correctly in the charts.

I rigged up a "T" connection with the sensor and a mechanical gauge to verify calibration.
I actually use the sensor to monitor fuel pressure.

Maybe the 02 Fbody OS won't allow this. I can't speak to that.

Chase, measure the voltage at these three pins. One should be 5v. One ground and the other is the output from the sensor. Hopefully you have the pinout of the sensor.

Ron, all appears to be working so far after plugging in the new sensor. Take a look at my log I posted above and tell me what you think.

When there isn't a sensor plugged in it seems to default to -15.7 PSI. With the old sensor plugged in it reads 130 PSI all the time so the sensor has shorted out or something. With the new sensor plugged in, it reads 0 PSI (or nearly 0) with the engine off and then reads 32-34 PSI after starting. There doesn't seem to be any conversion math required?

Do you have any pictures of your T fitting you built? I was just thinking about doing that. I'm going to hit the hardware store and see if I can find something in the plumbing section that matches the metric thread pitch of the LSx oil pressure sensor.

We were replying st the same time.
Glad it's working!

I'd assume your LS3 sensor is the same as LS1 and is a 130 psi sensor. So no math needed.

The "T" I built was just for testing. Remember, I was setting up a fuel pressure sensor.

For a mech gauge, you can just buy an adapter from Autometer and use the galley plug located at the left front of the block under the alternator.

Thank goodness for this thread. I searched for a couple days and finally found someone explaining that this does actually work.

Somehow my luck worked out for once as I believe I have an '00 Vette 0411 PCM. :D

You might need to enable it in the tune:


https://cimg8.ibsrv.net/gimg/ls1tech...22f9f5f8a2.png

Hey I'm glad that I could offer a little back to the community. It's usually ME asking for help with my stupid noob questions I have to ask in order to keep learning.

But yeah, I'm running a 411 PCM with a BLU/GRN harness that I converted to BLU/RED...... The original OP sensor I had was shot, replaced the sensor and wired it to the respective pins at the PCM and Voila!!! Datalogging oil pressure!!!!! I didn't have to do anything else becuase the layout files that Ron shared with me already had that provisioned.

So yes, you should be able to do this with your 411 PCM as well. Just wire it up to those pins at the PCM....

So i could get this working on my 99 trans am?

I can't say with absolute certainty, but I would say, more than likely. My 411 PCM that is logging oil pressure is from a 2002 F Body so....

Reviving an old thread, but was curious as well. I have an 02 LQ9 and would like to have the oil pressure on HP Tuners but also available on my OBD2 stream. So, I understand adding the wires/pins to the PCM harness and getting the correct sensor, but when you are logging Oil Pressure in HP Tuners, did it “know” it was oil pressure, or did you create a custom readout? In other words, is the computer recognizing it as oil pressure and thus it likely available on the serial OBD2 line?

I have custom gauges that use the OBD2 through the computer, and it’d be great if oil pressure was on the stream to avoid running its own sensor to the gauges.

Just add oil pressure in the channel list.
HP Tuners scanner uses the OBD2 data stream. So no reason your gauge thing shouldn’t pick it up.
You will just have to try it

Unless it’s not in my data stream since it wasn’t there from the factory... Agree, I’ll just have to try it, but it’s kinda an experiment I’d rather not do for nothing (buy a sensor, wire it into PCM, etc. only to end up using the different style Dakota digital sensor that came with the gauges. But you’re right, I’ll just have to try. Was hoping someone with an early truck 411 PCM might have tried this already.

Ok, what happens now if you try to select it? Does it show up? Or not. If it does, I would assume it reads 0.

I’m not even close to that point right now. Building my engine and harness currently, so I’m just trying to prepare. I’m wondering if I need to add oil pressure in the tune itself in system settings...

Got ya.
i went and looked at my current tune vs the orig read (99 Camaro OS) and I did indeed activate Oil Pressure in the System table.

Been a long time since I did this.

Ron

I know you said it had been a while, but do you recall if that was needed to get it to work? Like maybe it didn’t work pinning it alone, but flipping that switch and it did? I’m just wondering if that’s a feature hp tuners added later in system settings, and thus the old posts saying that the re-pinning didn’t work for some people.

I’ll throw a spare ecu on the bench and try to test it.

So i tested this. Of course I dont have a sensor hooked up, but HPT shows Oil Pressure as supported for an F body on a stock tune file.
With or without enabling Oil Pressure in the System Tab.

This is all I can help with. It's worked in all the harnesses I've added it to. If HPT can read it, Id think your dash thing would too.

Good Luck

Thanks.

I hope you report back.

I suspect it will work because the truck PCM is the same as the Holden PCM's of that era and I am using one of those and oil pressure works for me in HP Tuners.

I also run RealDash with an OBD2 bluetooth adapter on the OBD2 port, mounted a 6" screen for extra gauges, and have oil pressure and water temp gauges on the screen running off the PCM data, works great.

I’m beginning to doubt this will work for a truck pcm. I looked at the corvette oil pressure pin assignments, and one of the three is used for something else on my truck pcm (specifically it’s a front oxygen sensor ground). On the F body cars, they are open.

I'll give you a link to the holden PCM pinouts so you can compare where the pins are on those.

https://phantombullet.net/files/Hold...M-Pinouts.html


Maybe you could 'write entire' and install a different operating system, like the holden or vette one. But id ask to make sure its a compatible OS to your PCM.

https://www.hptuners.com/help/vcm_ed...menu_write.htm

I guess what I said earlier isnt necessarily the case because the PCM's can be the same, but the operating system can be different.

Thanks. Pin 63 Blue is where mine is different for oil pressure. That goes to my O2 sensors. I’m hesitant to write entire too as I don’t want to possibly mess up my drive by wire setup. The LQ9 uses a different pedal and TAC than the corvette one.

Stock harness or aftermarket?

Really either as I’m pulling unneeded pins from the factory one, but stock originally.

I added this to another 0411 with a Camaro OS recently.
Aftermarket harness, and they used the oil pressure ground for O2 ground as well.

I spliced the oil pressure ground to the O2 sensor ground.

Worked fine. We are actually is to measure converter cooler line pressure.

GM changed O2 sensor grounding even pre P59. The earlier harness didn’t use that ground

Thanks. That’s promising. I’ll give it a shot, but am concerned that my truck’s OS won’t have it in the OBD2 stream.