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SCR problem, kinda technical

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I have a 2012 chu613 with an MP8. I have a fleet ranging from 08 to 14. I'm working on one with a spn 4094-1 dtc and the guard dog states evaluating def quality 5mph derate temporarily off continue driving or something like that. It has new nox sensors, dosing module, nozzle and air regulator back by the air drier. I've cleaned and tested def dosing unit and replaced def filter. On tech tool when choosing what system I have while going to regeneration screen  it asks mp8 us 10 and mp8 without turbo bypass. I've tried both settings and can't get the dtc to go inactive. It seems that the temps are getting to normal range on both. But on mp8 us10 it shows turbo bypass and the green light never comes on. What I'm unsure about is, I have some with the dosing module on the left side of the engine with and without the bypass valve. I'm not sure if the bypass is suppose to activate on this one or maybe needs a software update.

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The code won't go inactive until it goes thru it's checks with the 5mph derate temporarily removed. Drive it like that for 30 minutes or so and it will either clear out or tell you it's going to derate again.

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Will do. I've had many clear out after a parked regen. Maybe this particular one's software won't allow it.

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Ya I always try the regen first, sometimes it works for me and sometimes not.

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This is a diagnostic flow chart  for fault SPN:5394/SPN:4094. Even though your fault is only 4094 it is the same thing basically.  Practically anything can cause the 4094 fault from contaminated DEF to plugged EGR  diff. psi sensor ports. The flow chart will have you test/check each system to verify it is functioning properly. 

snm 13- 022 archive spn5394 fmi17 diagnostic.pdf

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Yup and the key to it is do the cheap and easy and most likely  stuff first as always! Most of this stuff now has a track record not necessarily spelled out in order of Reliability! 😡

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Kinda off topic here but we do quite a bit of work on paccar engines. You wanna talk about an SCR nightmare, wow.

I had one with a def quality fault that just would not clear. I threw everything under the sun at it, nox sensors, def doser, new def fluid, dpf filter, catalyst, 7th injector, countless hours of troubleshooting and test driving all to no avail.

Ended up opening a case with paccar engineers and after several regens and 2 40 mile test drives that had to be recorded and send to them, they simply gave me 24 hour special access to a feature in the software that allowed me to clear the code out.

I mean really? After all that, it was that easy? I wish they'd give me that special button permanently!

The truck worked fine after that for about a year, then the same crap started again. The customer said screw it and had it deleted, and I don't blame em.

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That special button was likly an overlook me software probably not legal but a get out of jail free card for now to give them time to figure out what to do! 🙄 

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