Cummins ISC Oil Pressure Sensor

[Krash]

I come and read this forum so often to get answers to my questions, but seldom ever get to contribute to others problems. I thought I would change that by offering my experience on a recent problem.

I have a 2002 Diplomat with a 330 hp ISC 8.3 engine. It has served me well so far. I do all of my own maintenance and repairs when possible.

Recently after about a month of having the motorhome parked in one spot, we traveled about 90 miles from Denver up to the mountains. Upon traveling west and starting to climb the first grade, my engine warning light came on. I decelerated and started to pull over, then saw the light had gone out. I accelerated again and as soon as I got enough speed up for the transmission to up-shift, the light came on again. This continued, but I found by downshifting and keeping the rpm at about 2,000 the problem could be managed.

Getting to the point a little quicker, this problem has gotten worse during our current trip. I have Silver Leaf running so I see that I am getting a PID 100 – Low Oil Pressure code. However, I also have a dash oil pressure gauge which shows oil pressure is normal, so I don’t believe I have low oil pressure. Also, engine is running great.

Next phase: While watching everything closely as we drive along, the problem is getting worse. I have to keep the engine at 2,000 rpm even on level roads to keep the warning light off. Researching the problem on this and other forums, it seems my issue could be the oil pressure sensor. Apparently they go bad often and many were replaced with a device referred to as a switch back in 2004-2006. The switch seems to act more like an “idiot light” in that you either had oil pressure or not. No real oil pressure reading, just on/off.

So I keep driving because I have also found that the engine can probably be operated fine with the warning light, but I should be careful if the “Stop Engine” light comes on, because it could be followed by a complete engine shut down to protect the engine. Of course, while driving on a narrow road in the middle of Texas, the “Stop Engine” light comes on. There is no way I can stop on the road. No place to pull over. I am about 30 miles from Odessa where I know there is a Cummins shop.

Luckily I made it in, and they have time to take a look. I told them that I thought it was the oil pressure sensor. They kinda said “We’ll be the judge of that”, and two hours later confirmed that was indeed the problem. They ordered the part and let us stay in their yard overnight. The part came in, was installed, and cured the problem completely.

Now for the part that may help some others. I am not sure what was going on back in 2004-2006 with all the post saying that the replacement was a switch and not a real pressure gauge/sensor, but the part I got seems to be a direct replacement for the original part. It has three pins that mate up to the original Cummins connector.

The sensor cost about $95 and the part number is 4326849. It does give actual pressures to my Silver Leaf and tracks surprisingly closely to my dash oil pressure gauge, which is a completely separate gauge and sending unit.

This is definitely a very easy fix, which I would have tried if I were not traveling at the time. But the Cummins shop in Odessa did a good job at a reasonable price.

Hope this may help someone.

[CountryFit]

thank you for sharing!
i'll keep a close eye on it on my isc and change it as necessary.

[4Fingers]

Thank You

I really appreciate the information.

Don

[nehog]

A picture of the location of this sensor would be great. That would give anyone all one needed to know to do an emergency repair if this were to happen.

[llib enad]

After a year of trying to find the source of a oil leak, finally found it was the oil pressure sensor. It is above the starter, mine has 3 post but only 2 are used. My coach has 210,000 + miles , so the sensor lasted a long time.

Bill Dane
99 Country Coach Allure
ISC 330 hp

[Krash]

Originally Posted by llib enad

After a year of trying to find the source of a oil leak, finally found it was the oil pressure sensor. It is above the starter, mine has 3 post but only 2 are used. My coach has 210,000 + miles , so the sensor lasted a long time.

Bill Dane
99 Country Coach Allure
ISC 330 hp

Yep, it is just above the starter with a weather proof plug attached. If I can post a picture here, without have to link it from another site, I will take one in the morning and get it posted.

[Krash]

Here is what the part looks like. May not be the exact part, but looks just like this.


And here is where it is located on the engine. It is number 11.


If these images do not show, I guess you can go to the links listed to see them.

***Sorry, looks like that didn't work at all.

[Vanwill]

Originally Posted by Krash

Here is what the part looks like. May not be the exact part, but looks just like this.


And here is where it is located on the engine. It is number 11.


If these images do not show, I guess you can go to the links listed to see them.

***Sorry, looks like that didn't work at all.

Krash,
I also have the Silverleaf setup, using a tablet computer as my readout. It has always reported a steady "113 PSI", although my analog gage, like yours, displays the correct pressure. I have read repeatedly about what you mentioned--that at one time in the early 2000's Cummins had some recurring trouble with the oil pressure sensors they were using, and replaced them under warranty with a pressure-activated "switch", which was either "on" or "off". I wanted to replace mine with a sensor instead of a switch but never did so. The reason I did not is that I also read repeatedly that when Cummins changed from sensor to switch, there had to be a parameter re-written in the Cummins computer to get it to accept an on-off sensor, and that if I replaced the switch with a sensor, I would get a constant "Low Oil Pressure" signal, and the engine might shut down.

I can't say that I've ever read this info from a Cummins source, but it was repeated so often on this, and other, forums that it is likely true.

Just a warning to be careful when replacing your oil pressure sensing "device"--a type different than the one you have presently might cause a problem.

[ladagobago]

You are right about the switch. It is called a binary switch. Same switch used in most vehicles to indicate a low or high something. The are available either normally open or normally closed. The also are avaialbe in various pressure or temperature settings.

As for cummins. at least on my 99 ISB the gauge sending unit went bad and cummins was unable to replace the original. The supplied a part number for the binary switch but I had to go to a freightliner dealer to have it installed with a new wiring harness and reprogram the ECM to see the on off condition. the switch is a 5 pound switch which is the minimum pressure allowed for operation. I went to a white truck and blue bird bus facility as the labor was less.

Now my pressure gauge stay right in the middle. I would have preferred a light as I don't constantly watch the needle.

[Krash]

UPDATE**
Sorry this took such a long time to post, but the replacement of the oil pressure sensor by Cummins has not gone as smoothly as I indicated above. After driving a few more times for a few hundred miles, the Silverleaf readout changed from tracking close to my oil pressure gauge, to only displaying two readings when the engine was running. It only displays 101 psi, and 50 psi. This is similar to what others described as the binary switch.

As soon as this change occurred, my warning light came on, and has remained on. I have had no choice but to drive it for several hundred miles with this condition over a few days time.

My Silverleaf is now showing a code of PID 100 - Engine Oil Pressure – Low Voltage.

I called the Cummins shop that installed the sensor, but they just said they didn’t know why it was doing this, and I should bring it back in. I suspect it might be one of a few things.

1) Maybe they installed the old type of switch that was not the binary version, but they updated the software which now thought the binary switch was installed?

2) Maybe they installed the new binary type of switch, but didn’t update the software?

3) Maybe whatever type of switch was installed, it simply failed after a few days?

They did update the software before they did any work on the engine, something I didn’t ask them to do, and I wish they hadn’t done. But, they said it hadn’t been updated in a long time and should be done.

Not sure how I will proceed now, but will post any new info when I make some progress.

[ladagobago]

Part of the conversion to a binary switch also included a change in the wiring harness. This is supply the 12 volt and change the connection on the ecm. they may not have made a good connection. the switch only transfers the 12 volts or no volts.