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2018 MRU MP7 Nox


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Got a 2018 Mack MRU with an MP7. Truck has had regen issues since we got it new, been to the dealership multiple times but Mack says they can’t duplicate the issues. 
 

Active codes as of right now.

P103C00 P20EE00 P046C64 P24F700

Truck is in derate requesting a Sulfur regen. During the regen the Nox inlet is at 1026 PPM and outlet is 1773 PPM.

 

It’s had the SCR box, DPF, DOC, DEF filter, DEF doser, DEF level sensor replaced.

 

Any suggestions on where to go next?

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Yup start at the other end! make sure you got proper temp ! Turbo spooling properly on regen ? Check turbo Effort possibly sticking ! fuel pressure OK? fuel dowser clean?Dpf sensor ports clear  tubes clear? with this junk you need to work front to back ALMOST always!

 

Just sayin

Edited by fjh
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5 minutes ago, fjh said:

Yup start at the other end! make sure you got proper temp ! Turbo spooling properly on regen ? Check turbo Effort possibly sticking ! fuel pressure OK? fuel dowser clean?Dpf sensor ports clear  tubes clear? with this junk you need to work front to back ALMOST always!

 

Just sayin

Turbo bearings went out about a year ago, had a new turbo and actuator installed. Fuel pressure is good. 7th injector is clean, gets replaced annually. DPF sensor ports and sensor are clean. EGR pressure sensor and ports are clean as well.

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hmmm from what I have seen these are reasonable Look not bad ! duno what to tell ya!

Was there any evidence of crystal buildup when they had the box off!?Thinking about a crack in the ash can! quite a common thing Also the nox sensors were  chronic on these at one point they had a point where we had been changing them left right and center!

You could throw sensors at it looks like they have thrown everything else at it! they could be out of parameter and I believe you must do a learned data reset! 

Edited by fjh
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I’m really surprised you didn’t put nox sensors on it. Not gonna say that’s the answer, but at this point why not?

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Nox level is higher on the outlet than the inlet. Try an outlet Nox sensor and perform the regen. Make sure you reset learned data as mentioned. It is true that these sensors were and still are failing.

V

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if I may..?  shouldnt T-1 be around 850 degrees? Its been years since I did a forced re-gen with PTT..  jojo

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It is a Nox issue that is throwing fault codes and preventing the truck from being able to do a regen by the button and putting it into limp mode every couple weeks. There is no DEF build up. The Nox sensors have been replaced 3 times in the past 2 years with no change on the values. The Nox outlet has always read higher than the inlet.

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10 minutes ago, springerj10 said:

It is a Nox issue that is throwing fault codes and preventing the truck from being able to do a regen by the button and putting it into limp mode every couple weeks. There is no DEF build up. The Nox sensors have been replaced 3 times in the past 2 years with no change on the values. The Nox outlet has always read higher than the inlet.

Just note that these sensors can be effected by dampness I believe they had us move the outlet sensor on several trucks further back away from the y pipe water coming down the stack!

Just sayin! 

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22 minutes ago, springerj10 said:

I don’t remember what it was at this time, I’ll check after the truck comes back in.

Bro if you look at the soot value there If you can believe the screen shot  it looks to be working fine!

just sayin!😐

These dam aftertreatment systems are a crap shoot to trouble shoot  no real cut and dried tests bunch of parts changing BS!

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55 minutes ago, fjh said:

Bro if you look at the soot value there If you can believe the screen shot  it looks to be working fine!

just sayin!😐

These dam aftertreatment systems are a crap shoot to trouble shoot  no real cut and dried tests bunch of parts changing BS!

That’s what I was thinking about the soot level…is it possible it needs some kind of update?

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