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JCTech
JCTech, Diesel Mechanic
Category: Heavy Equipment
Satisfied Customers: 387
Experience:  31 years experience as a Diesel Mechanic, 14 years at Cummins, good with electronic control systems
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I have a cummins N14 plus motor. I am having a problem with

Customer Question

I have a cummins N14 plus motor. I am having a problem with the engine turning itself off. The engine warning light comes on followed by the stop engin light and then the engine shuts down. It is not the computer as I had it sent in to a company to goes through them and they said it was one of the best working computers they ever saw. Any ideas on what else it can be.
Submitted: 2 years ago.
Category: Heavy Equipment
Expert:  JCTech replied 2 years ago.
Hi,
This does not sound like an ECM issue
What service tool were the shop using to troubleshoot the engine problem?
Any active or inactive fault codes in the ECM?

John
Customer: replied 2 years ago.

My mechanic plugged a machine in the dash and it kept throwing out numerous codes which the mechanic told me was saying it was a bad ECM. so I sent the ECM to a company in illinois who checked it out and said that there was nothing wrong with the ECM. The ECM tech called my mechanic to discuss what codes the mechanic found and the ECM tech stated that those codes identified by my mechanic are not even codes for a cummins motor.

 

One of the codes identified a problem with crankcase positioning sensor. mechanic replaced this and codes kept indicating it was bad. That was part of reason mechanic said it had to be the ECM.

Expert:  JCTech replied 2 years ago.
Hi,
There are several failure modes that can shut down the engine, the engine position sensor is one of them, however replacing the engine position sensor by itself is not the correct troubleshooting procedure, your mechanic must first check the wires for the engine position sensor in the engine wiring harness, to be sure that he is repairing the correct component. Just jumping in and replacing the component without checking the rest of the circuit leads to expensive and incorrect repairs, the most common failure of the engine position sensor is moisture in the connector.

The crankshaft position sensor itself has two coils in it, so you would have a warning lamp for the failure of the first coil but the engine would carry on running without derate, on the second coil. I have never seen both coils fail simultaneously, although in theory it could happen.

Multiple fault codes that keep appearing and dissapearing (in a short period of time) can be a symptom of a problem in the wiring harness or power supply to the ECM.

When advising fault codes be sure to identify whether they are Cummins fault codes, read with Cummins Insite (or a generic reader with translate functionality), or the SAE J1939/J1587 fault codes that most multi engine service tools read. For example an SAE J1587 code SID 115 (engine oil change interval) is not the same as a Cummins code 155 (engine position sensor). Your mechanic should understand the basic difference between the J1939 and J1587 datalinks and what this means when viewing the fault codes.

Your engine can be configured to shut down on engine protection parameters, low oil pressure, high coolant temperature and low coolant level.
An amber warning follwed be a red stop lamp and the engine stopping would be correct for any of these 3 parameters, and an engine position sensor fault

Your engine can also have excessive idle time set up as a shutdown parameter, although I think you would be aware if this were the case. The amber lamp flashes for 20 seconds and the engine shuts down.
There are no sensors in the fuel system, so you would not get a red or amber warning for a fuel system fault

Hope this helps
John
Expert:  JCTech replied 2 years ago.
Hi,
My advice would be to refit the ECM, clear ALL the fault codes before starting the engine.
Record the fault codes that are present after the engine has shut down, also record the order in which they occurred (not displayed on the screen) and the number of occurrences of each, do not turn the keyswitch off between the engine shutdown and recording the fault codes.
let me know and I will offer my advice.

Hope this helps
John
Customer: replied 2 years ago.

I plan to give this information to my mechanic on monday.

 

Also was wondering what you thought of possibility this could be a sensor problem.? Is the sensor the same for both the high coolant temperature and low coolant level as mentioned above?

Expert:  JCTech replied 2 years ago.
Hi,
It is possible that this is caused by a sensor problem, what we call an "in range failure"
The ECM knows the difference between a "dead" sensor, a broken wire(or other wire fault for a sensor) and a good sensor, a dead sensor has no signal, and a broken wire or short circuit in a signal or volt supply wire will result in an "out of range" signal. In either of these cases the ECM will give the appropriate fault code and ignore the signal from the sensor and use a default value.
With an "in range failure" the sensor gives a signal that is within the allowable value for that sensor, but is incorrect. A bit like the sensor is stuck low, high or in the middle, for example, your engine may have good oil pressure, but the oil pressure sensor has failed in a low state and is giving a signal for 5PSI oil pressure, you will have a fault code for low oil pressure, a red warning lamp, and if configured for engine protection shutdown, the engine will shutdown. The same can happen for the boost pressure sensor, I have never seen it happen to a temperature sensor.
To diagnose this type of failure, use Cummins Insite, (or a generic tool that can monitor the sensor data) monitor the oil pressure with the engine stopped, it should be 0 PSI, start the engine and you should see the oil pressure climb as the engine is started. Use a known good mechanical gauge to verify oil pressure is present, or a calibrated mechanical gauge to verify the accuracy of the sensor. The same applies to all the sensors check temp sensors with the engine cold and then hot.
If oil pressure is the same with the engine stopped and running, there is an issue with the sensor, the same applies to the temperature sensors. The low coolant level sensor can be checked in a similar manner.
The fault codes will tell you what caused the engine to shut down, you can then investigate that system.

Hope this helps
John

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