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+--- Thread: Isx unknown derate (/showthread.php?tid=10120)
Isx unknown derate - Papa_Buck - 05-10-2025
Hello all
I am getting a new derate screen that I haven’t seen before so I thought I would ask the professionals here since the stealerships are useless.
The derate doesn’t specify how much derate and there are no faults or check engine codes or lights. This is a plain isx 2250 that is not demandated and not modified in any way. Dpf can replaced 2 months ago as was the egr cooler. Engine has not thrown any fault codes for a long time, until this.
Any thoughts on what caused this will be appreciated, pic of derate attached.
Thanks
RE: Isx unknown derate - Rawze - 05-10-2025
Insite should show you what the derate is for.
RE: Isx unknown derate - Papa_Buck - 05-10-2025
There are no faults in insite. Is there a way to watch the ecm logic?
RE: Isx unknown derate - marek4792 - 05-10-2025
Have someone check the engine state monitor on Insite while going down the road, it should tell you why it's pulling air/fuel back when it derates.
RE: Isx unknown derate - windowrattler - 05-11-2025
Pretty sure that would be some type of scr/Def system issue with a countdown like that. It's surprising that it doesn't have some type of code though. If it was happening I would be looking at nox sensor readings/conversion, Def parameters like pump pressure, tank level and whether or not its injecting Def.
RE: Isx unknown derate - Rawze - 05-11-2025
maybe also post a screen shot of the regen history in Insite.
maybe the cans are getting clogged up by excess soot production due to dirty sensors??.
When is the last time you did a thourough EGR Tune-up on the enigne?
info: https://rawze.com/forums/showthread.php?tid=842&pid=7030#pid7030
RE: Isx unknown derate - Papa_Buck - 05-11-2025
Update problem solved
Thank you everyone for your suggestions. With the help to monitor the egr sensors, the problem resulted in the pressure sensor (which was only 3 months old) sending random values. Watching the sensor it would send random numbers all over the place. I guess that’s why the computer couldn’t decide on a derate percentage or time. I replaced the sensor and the derate instantly went away. I am still not sure why the faulty sensor didn’t generate a fault codes or cel.
Thank you everyone
RE: Isx unknown derate - mikkhh - 05-12-2025
What about the faulty part? Was it genuine OEM part or aftermarket garbage?