CM2350 derate 6255 only no fault codes

[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.

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#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.

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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.