Cummins "Temporary Fix"

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rsalhus

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We have a 2001 Rexhall Vision DP motorhome with a Cummins ISB engine that we bought used from an RV dealer in September, 2005 when it had 19K miles on it.  We love the motorhome, but amongst the paperwork that came with it was what appeared to be a recall letter from Cummins dated October, 2001 addressing a problem with incorrect oil pressure sensor readings.  It seems a limited number of new motorhomes built at that time had faulty oil pressure sensors that were sending false oil pressure signals to the ECM (Electronic Control Module) with Cummins ISB, ISC, and ISL engines.  Apparently our motorhome was one of them.

I didn't think much about that recall letter until recently when I was reorganizing all the documents associated with the motorhome and decided to read it a little closer so I could decide how to file it.  The letter went on to say that Cummins came up with a temporary fix to put a constant resistance into the oil pressure sensor circuit to make the ECM 'think' that the oil pressure was OK.  So, in effect, the oil pressure guage reading was hard-wired to read 'good' for those motorhomes that had the temporary fix installed and wasn't displaying the actual oil pressure at all.  Owners of these motorhomes were apparently directed to an authorized Cummins Distributor/Dealer to have the temporary fix installed. 

The recall letter went on to state that Cummins would maintain the warranty responsibilities as stated in the motorhome's Owner's Manual.  I assume the previous owner of our motorhome had the temporary fix installed and must have filled out the information card and sent it in so that he would be informed once a permanent solution was developed.  I then searched through the rest of the paperwork we inherited for something to tell me that the permanent solution was eventually implemented.  I found no such paperwork.  Maybe he got the notice afer he sold the motorhome, I don't know.

Then I got to thinking, our motorhome's ISB engine has always shown excellent oil pressure, and in fact, I don't remember seeing the oil presssure drop appreciably when idling or increase when starting out from a stop.  I have a considerable amount of diesel truck driving experience and am aware of how much and how often diesel oil pressure readings change.  What if the previous owner received the notice for the permanent fix and did nothing about it?  What if they never installed the permanent fix in our motorhome? 

Now I was getting a little concerned, so I called the Cummins Customer Assistance Center and asked the guy there if he could answer my questions.  I gave him our engine serial number and when he came back from his search, he informed me that our motorhome indeed had had the temporary fix installed but there was no record of the permanent fix ever being installed.  He gave me the number of a local Coach Care center and said I should call them and make an appointment to have the permanent fix installed.  So I called Coach Care immediately and after discussing it with several people there, they ended up telling me that I would have to pick up the cost for this fix because the two-year period that was set up for this particular recall had expired as of December 31, 2005.  I called the guy at the Cummins Assistance Center back again and he said he would see if there is something else he can do to help me, but that was two weeks ago and nothing else has been done.  I keep calling back to see if he's found out anything but all I've gotten is the run around.  It looks like I'm stuck with the cost of this fix. 

Incidentally, it looks like Cummins started installing the temporary fix for this problem as early as October, 2001.  But it appears that a permanent solution wasn't implemented with a recall until January, 2004.  So even though it took them more than two years to come up with a permanent solution, they setup the recall to expire in exactly two years.  And they won't make an exception for those of us that got caught with the temporary fix installed but with no notification of the permanent fix recall.  To me, it was their problem from the getgo, so why should I be charged to fix it?
 

BernieD

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Rolf

If you get varying readings on your oil pressure gauge, you still have the original oil sensor. The fix when Cummins was having the oil pressure readings problem was to replace the sensor with an oil pressure switch. There are only 2 positions on the switch, on and off. When the switch stabilizes at start up your gauge will read something like 55 PSI and not change. The true oil pressure is maintained in the engine ECU and if a low pressure is identified, the engine derates or cuts off. With the sensor, as you said, the defective sensors would short out or something (usually before 6k miles) and send a signal to the engine to shut down and you could not restart it. Not all sensors were defective, I had a good sensor on my 2002 ISL that was replaced without my knowledge or permission. I finally got a Cummins tech at one of the FMCA conventions to get me a good sensor which he sent, I was responsible for installation. I too never got a notice of the replacement sensors being available.

I don't know if this will be of any help in replacing your "switch" but you may still have the original sensor which needn't be replaced..
 

rsalhus

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Bernie,

I don't get varying readings displayed on our oil pressure gauge.  It immediately goes to 55 or so and stays there.  We still have the temporary fix in our motorhome and have no related switch installed (that I know of).  Was the switch installed on the dash?

I don't understand the purpose of the switch.  Is it to turn on and off the real oil pressure display?  Or is it to send a false reading (when on) to the ECM to make it think the oil pressure is good so that it can be restarted after the ECM shut it down?  And what do you mean by "when the switch stabilizes?"  I think you meant to say "when the oil pressure stabilizes" didn't you?  And how can the ECM know the real pressure when there is no oil pressure sensor in the circuit?
 

BernieD

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Rolf

Sorry, I wasn't clear about the switch. The reading unit on your engine was a sensor, it "read" the pressure of the oil and sent a reading to the dashboard gauge. The switch that I was talking about replaced the sensor, so once your engine, when turned on and started to develop oil pressure, it sent a signal to the gauge that there was oil pressure. The reading was strictly yes or no, on or off. When it has a reading, your gauge reads 55 PSI. Effectively you have an idiot light in analog form.

As to the ECM, there apparently is another sensor somewhere because the Silver Leaf reported the actual oil pressure.
 

rsalhus

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Bernie

Thanks for the clarification.  I think I'm beginning to understand what Cummins is doing here, please correct me if I'm wrong. 

The problem started when Cummins detected a defective oil pressure sensor in some of their diesel engines.  The defective sensors sent erroneous signals to the ECM which resulted in shutting the engine down, without allowing it to be restarted.  Cummins couldn't come up with an immediate fix for the defective sensors so they issued a recall to install a 'temporary fix' which replaced the OEM sensor (there are actually two sensors in the system, the other one feeds the ECM directly) with a resistor network that sends an artificial signal to the ECM which 'fakes' a good oil pressure signal.  (As I understand it, this 'temporary fix' prevents the OEM sensor from actually detecting a loss of oil pressure and sending that information on to the ECM, but the ECM can still detect a loss of oil pressure from it's own sensor.)

Cummins apparently never came up with a reliable sensor to replace the defective OEM sensors. (Why couldn't they use the same sensor for the OEM sensor as they use for the ECM?)  Any way, they ended up with a 'kluge' for the permanent solution.  The 'kluge' is basically a switch that replaces the sensor.  When a certain oil pressure is reached after startup, the switch is turned on which sends a certain signal to the ECM (and an artificial 48 PSI reading to the oil pressure gauge on the dash) which tells the ECM that there is valid oil pressure.  If no oil pressure is detected, the switch is effectively turned off, and sending that signal to the ECM results in the ECM derating (shutting down) engine power. 

From the motorhome owner's viewpoint, the oil pressure gauge is effectively relegated to an 'idiot light' when the 'kluge' is installed.  It will either read zero PSI when there is NO pressure, or somewhere around a constant 48 PSI when there IS oil pressure.  So what does the 'kluge' do for me and why should I pay to have it installed?  Well, it will show me a zero on the oil pressure gauge when the ignition key is turned to 'on' but not to 'start'.  (It currently shows 48 PSI in this state with the 'temporary fix' installed.)  I guess I don't really care to pay for this feature.  But how about a sudden loss of oil pressure while driving down the road?  I would think the OEM sensor would detect that and signal the ECM accordingly (as well as displaying zero PSI on the oil pressure gauge).  But the ECM has it's own sensor and will detect the loss of oil pressure on it's own, right? 

The only thing I can figure out is that maybe the combination of both sensors detecting a sudden loss of oil pressure might result in a faster engine shutdown by the ECM.  Otherwise, there wouldn't be any real advantage in having the 'kluge' installed, would there?  Would a driver be able to notice that the oil pressure gauge is reading zero in the 15 seconds or so that it takes to derate engine power after he notices that something is wrong (lights flashing and alarms going off)?  I think I would be concentrating more on getting the motorhome safely off the road than trying to understand what was really wrong during those 15 seconds, don't you?
 

BernieD

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Rolf

Couldn't have said it better myself :D :D tho my kluge read 55 PSI. In it's current condition, the kluge doesn't do anything, the ECM sensor controls everything directly without waiting for the kluge. Personally, I would prefer oil temperature and oil level gauges like I had on my Porsche, but IMHO, the oil pressure readout could be replaced by an idiot light.
 

rsalhus

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I heard from the service manager at the local Cummins place today.  Now he tells me that there is only one oil pressure sensor in my motorhome and it (as part of the 'temporary fix') is currently sending an artificial signal to both the oil pressure gauge and to the ECM, indicating that the oil pressure is a constant 48 PSI.  So if I currently were to lose all oil pressure in my engine for some reason, neither me (via my oil pressure gauge) nor the ECM would ever know about it and the ECM would not shut the engine down because of a loss of oil pressure.  (How they could ever install such a fix is beyond my realm of thinking!)

The permanent fix that they have developed provides a little more protection.  Upon startup, the new sensor will 'read' the oil pressure and will send a constant 48 PSI to the ECM if it senses oil pressure.  If it does not sense oil pressure at startup or at anytime that the engine is running, it will send a signal to the ECM which will turn on the red 'Engine Fault' light and derate engine power. 

The oil pressure gauge may or may not show anything with the permanent fix since it is an OEM device and not supported by Cummins.  It may show a constant 48 PSI when there is oil pressure or it may show 0 PSI all the time, I won't know until it is installed.  But it won't show the 'true' oil pressure in any case and I will have no option but to pay half of the total cost to have this installed.  Should I feel cheated by Cummins or glad to pay for some protection against the loss of oil pressure?
 
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