CM2350 derate 6255 only no fault codes

[greg1227]

We have a customers truck 2018 Cummins CM2350 ISX 15 in the shop has been having derate messages popping up . Plug in Insite and see inactive 1659 fault 1 count . Clear code comes back on a day or two later . Was able to get him to leave the truck for a while and tried for hours to get code to come on . Finally yesterday did 2 injector performance tests and 30 seconds after 2nd test ( passed ) the 1659 fault is on and active 1 count . Display reads derate in 30 minutes . Truck is running perfectly no skips at all . Truck goes into derate , still 1659 fault active and 6255 inactive still 1 count on 1659 . Cleared all codes only active 1659 clears and 6255 goes active . Shut truck down for the night come in today and start truck , 6255 was now inactive cleared the fault . Did performance test for injectors and revs up and then drops back to idle and 6255 fault inactive comes on. So far we have checked resistance in harness from ecm to valve cover , from valve cover to injectors. We swapped number 6 injector to 4 , we swapped the engine brake rocker with 5 ( theses steps were done a week ago between his runs and 1659 continued to come up ) Now can do injector cut out test, no issues, forced regen , air handling test all with no issue as soon as injector performance starts 1 second kicks out and inactive 6255 derate code is up . Thought i read somewhere on CM2250 some had similar issues and they changed the ecm . I was told this ECM injector drive controls multiple injectors and may not be the issue because it only happens to cyl 6 and only 1 count any help would be appreciated

[Rawze]

The faults that mentioned ...

Fault 1659 = Cylinder #6 misfire detection.

Fault 6255 = Torque derate is active due to other faults occurring. Is a generic fault that shows just about any time that there is a derate due to OTHER faults triggering.

==============

#1 is the engine de-mandated (deleted)?.
You did not mention this, and yes it would be a very relevent question. A lot of delete programs are complete s%it, and do things like fooling the ecm into giving up fuel, or jacked with power levels against the ecm's will, in ways that it should not be. things that would cause the injector mis-fire detection system to become unstable or too sensitive, and giving alarms in error.

#2 HAS ANYONE bothered to do a proper rail leak-down test on it AFTER everything was put back together again, exactly like this video shows?. = and if so, how many PSI did it drop in one minute?.
ref: http://rawze.com/forums/showthread.php?t...3#pid75483

> That test has to be done EVERY TIME someone messes with the fuel system, or the injectors, and any issues resolved.


#2 You said someone swapped injectors (4 to 6) and it stayed with cylinder #6.

- It could be the wiring harness in the head going bad, as they do get saturated with oil over the years and do cause issues like this sometimes.

- It could be the ecm wiring harness going bad external to the engine cover, or the plug at the engine cover saturated and causing issues too.


BTW: The engine uses the exhaust pressure sensor to detect misfire conditions ... by essentially "listening to the sound waves" coming from the exhaust pressure sensor, among other things. SO...

- It could be the exhaust pressure sensor circuit clogging up where it goes thru the thermostat housing. An extremely common problem for all model ISX engines.

- It could be the little "U-shaped" crossover tube between the exhaust manifold and the thermostat housing that feeds the exhaust pressure sensor circuit bad, leaking, or something wrong with it.

- It could be a bad exhaust pressure sensor, or someone installed an after-garbage brand on one on (seen a lot of this problem lately from dorman brand, and other non-oem sensors), and now its giving false alarms.

- It can also be an out-dated program for the engine, or a program that does not belong in the engine. MAKE SURE that the exact program according to the engine ser# is in that ecm.. AND that it is up to date within a year or so. The red engine maker has had a many of software updates that involve mis-fire detection over the last couple years, and it is important to have the latest software. Having mis-matched software can cause problems like this too.

- It could also be the valves out of adjustment, a flaked cam, or maybe the overhead cam slipped, all could make the mis-fire detection system too sensitive too.

=============

I.E.>
If it is de-mandated.. and since MORE THAN 90%+ OF ALL DE-MANDATES that people/shops use are absolute garbage out there ... that is the FIRST thing to have checked/corrected. Copy the file out of the ecm (using the Ct software) and e-mail it to me for a proper review of what someone did in that programming.

Eliminate it FIRST, as you cannot sort out an engine if the computer itself is fighting against you because something is unstable or too sensitive due to some redneck-hackery trash.

Next, is to also check what was mentioned above as well with the wiring harness, exhaust pressure sensor circuit by cleaning it out properly, replacing old exh.pressure sensor, etc.

[greg1227]

Thanks for the response
It is not de mandated all factory . We had replaced exhaust sensor recently ( month or so ) with a Cummins sensor . We have the latest ECM update from a friend with a factory Cummins computer . We did see oil in the valve cover connector so that will be something we will deal with . Did not do rail test will do that as well . We ohmd the wiring from ecm to connector at valve cover all exactly the same and wiggled wires during test . Will address all of your concerns on Monday when i get back to shop . Still wondering why it would show a single count for the misfire fault and then show derate in 30 minutes . Now no code except derate code and instantly when doin a injector performance test . Will do all testing Monday and get back thanks again

[Rawze]

(09-22-2023 )greg1227 Wrote:  Thanks for the response
It is not de mandated all factory . We had replaced exhaust sensor recently ( month or so ) with a Cummins sensor . We have the latest ECM update from a friend with a factory Cummins computer . We did see oil in the valve cover connector so that will be something we will deal with . Did not do rail test will do that as well . We ohmd the wiring from ecm to connector at valve cover all exactly the same and wiggled wires during test . Will address all of your concerns on Monday when i get back to shop . Still wondering why it would show a single count for the misfire fault and then show derate in 30 minutes . Now no code except derate code and instantly when doin a injector performance test . Will do all testing Monday and get back thanks again

Push comes to shove, if no one can solve it, someone might have to record the 'CBL_Fuel_State', engine mode control, and other settings in the ecm using the Clalterm software and some desktop recording software. Get it to act up under normal load conditions instead of that mostly useless injector performance test crap. This will at least reveal what manager or system in the ecm is controlling the derate condition.

[greg1227]

Did the fuel rail pressure test it dropped less than 150 psi in a minute. Not sure how to check what manager is controlling the derate condition .

[Rawze]

(09-25-2023 )greg1227 Wrote:  Did the fuel rail pressure test it dropped less than 150 psi in a minute. Not sure how to check what manager is controlling the derate condition .

with a screen setup like this in Cal$term...
http://rawze.com/forums/showthread.php?t...6#pid28636

[greg1227]

changed injector harness and 1659 and 6255 came active after idling about 1/2 hour

[Smooth]

Greg any luck with this, I have a similar issue in the shop now.

2019 Not De-mandated , when under a load truck will de-rate but not throwing any other engine code.

Same Issue , Running tests to attempt to reproduce the derate fault in Engine,
Injector Performance Test , Stops immediately throws 6255 Derate Fault with no accompanying fault.
6255 Immediately goes inactive afterwards

[Smooth]

Not solved this riddle yet, But more information as so many post go without answers or solutions.

I am on Day 4 of this issue. Truck has never been tampered with, All Factory components still there.
6255 Engine Protection Torque Derate Goes active and inactive when motor is under strain will not complete Injector Performance Test

Aftertreatment Engine out Nox Test - instead of Pass or Fail when attempt this test its Not Available

I looked under Data Monitor while truck is operating -
Aftertreatment Intake Nox and Aftertreatment Outlet Nox - Not reading all zero and under Stable line - READING NOT AVAILABLE

Now the part I cannot believe as coincidence - In may there was an updated Calibration performed, HD10361.10 Reduce the occurrence of FC3749
Shocker FC3749 is Nox fault for High Drift

Currently Trying to contact Cummins or figure out away to get HD10361.09 so can upload and see what changes.