Cummins ISX oil pressure sensor question

lockmup68 · November 24, 2016

After my 3600 mile trip to the rally, Casper, WY and back to TN, at the last stop about an two hours from home, I noticed a bad leak under pressure. I could not tell where it was coming from in the dark, so I checked the oil levels, and it was only down about 1/4 on the fill line, so I added it up to full and stopped about every 30 min and checked levels. Wasn't draining out too fast, but was making a mess everywhere underneath.

Finally tracked it down to an oil pressure sensor that was blowing out the back, top side of block, drivers side. Now for the question. The ISX has an oil pressure sending unit that plugs into the main harness. This is a second oil pressure sending unit. It was a two-wire unit that looks to be a GM part and has a stand alone harness that runs across the top of the motor and into the firewall behind the fuse panel on the passenger side.

I picked up a new sending unit with the right thread and pitch from cummins. The international part and the cummins part both are 3 wire units and with different weatherpack connector than the one that was in there. I found a pigtail with the right weatherpack connector on ebay, also 3 wire.

So now the fun part. Put the new sensor in, oil leak is stopped. without plugging it in to the harness, oil pressure gauge and temp gauge are working fine. No codes from the computer showing something is missing or an input is missing. I can try to wire up the 3 wire pigtail to the two wire harness that is there, but which two wires to use? I have traced it from the sensor to the firewall and then lose the wires behind the dash. The only way to figure it out would be to take the entire dash apart.

So my question is, since I have oil pressure and temp gauges working, no codes on computer, do I need to worry about it? It wasn't even a cummins or international part. At this point, I have a $50 cummins sensor being used as a plug. The mechanics say just to run with it since there are no codes and the gauges are working properly.

Please let me know your thoughts. Appreciate your help.

Shannon

Shifted · November 24, 2016

Personally, I would want to know for sure what it is and whether or not it should be hooked up. Are you sure that it's not a temperature sensor that was originally in there? The ISX should have both an oil temperature sensor and an oil pressure sensor. I doubt if you would throw any codes if the oil temperature sensor is disconnected, but it is part of the engine protection and emissions control system. So you may just end up with slightly worse fuel economy, or no effect at all, or it might fail to shut down the engine if there is an over temperature situation with the oil.

It's also possible that it is an add on sensor threaded into an unused port on the motor by a previous owner for other purposes?

Anyway, two suggestions...

One, consider using a wire tracker/tracer like this one: https://www.amazon.com/Gardner-Bender-Tester-Tracker-GET-4220K/dp/B000GAUXN8

I have one and it works well for these kinds of situations. You sound like you're on point with electronics, so it should be no problem hooking the signal generator up to the engine bay side of the wire and using the tone tracker inside the cab to find the other end.

Second, take a look at this ISX electronics manual: https://www.dropbox.com/s/olj3848ctu1pex2/ISX-02%20Electronics.pdf?raw=1

Pages 4 and 5 show the oil pressure and temperature sensors. Maybe that will help in identifying what's what and where it is supposed to go? Or, maybe it will help show what it ISN'T, and help narrow it down that way?

Please let us know what you find. I would be interested in hearing what the outcome is.

HERO Maker · November 24, 2016

Shifted,

That was real informative and appreciate the posting with pics.

I did notice that the oil pressure sensor had 3 wires, and the temp only had 2.

Good posting.

lockmup68 · November 25, 2016

oil temp and oil pressure gauges are working properly....

Thanks,

Shannon

Darryl&Rita · November 25, 2016

Possible aftermarket sensor to tell the Home Office? Tied into a Qualcomm system, or something similar? Time to start following wires.

lockmup68 · November 25, 2016

Possible aftermarket sensor to tell the Home Office? Tied into a Qualcomm system, or something similar? Time to start following wires.

Probably. I'm going to leave it right now. If something isn't working soon, I'll pull the dash out and trace further. Appreciate everyone's help.

Thanks and have a great day,

Shannon

lockmup68 · December 19, 2016

Update: So the sensor that came out is a pressure sensor, not a temp sensor.

So got a new pressure sensor from Cummins. Threaded right in. I found a pigtail on ebay and got that here. For kicks, we didn't hook up the sensor to the wire harness (2 wire; the sensor and pigtail is 3 wire). And the oil pressure and temp gauges are working fine. Every gauge on the dash is working, no codes in the computer. We traced the wires through the firewall to the dash, but the disappear in the back of the dash and I didn't have time to take the entire dash apart. However, all gauges are working and no codes on computer, so I have no idea that the sensor and wires were for.

So I'm using a $70 oil pressure sensor as a plug right now and I have a spare pigtail....Good news is no more oil shooting everywhere.

Shannon