Isuzu NPR regeneration

Jim Technician Dover, New Jersey Posted   Latest  
Unsolved
Driveability
Heavy Duty
2012 Isuzu NPR-HD 5.2L (6 4HK1)
Will Not Complete A Regen

I have this 2012 NPR, Im calling out more professionals for assistance, seeing as many of my die hards have left the mothership and came here. But I am stumped, my local Isuzu "lead tech" is stumped.

This truck came in with a p244b - dpf high differential pressure, p2463 - dpf high soot accumulation, p2459 - dpf regen frequency. I perform a forced selective regen. System goes 200 - regen start. Sits there awhile. then 220 - temp rise. Temps get to about 480* which is too low for the aftertreatment injector to be actuated. I kick it out and retry a few times. I step back and punt a DOC in it. I get it together and try a regen. It sits at 200 - regen start for an hour. Nothing happens. I take it out and beat it to get the exhaust hot, return and retry, it goes 200 - regen start, 220 - temp rise, then 370-regen active. EGT gets to about 800*, it goes BACK to 200-regen start and sits there half an hour, then kicks out and sets a P244C - too long in regen. I take out the aftertreatment injector to make sure it atomizes, and look in its hole. The injector is spraying through a tiny hole in about 1/4" of carbon. I poke through and clean it. Put the injector back in and try again, it goes in 200 - regen start, then 220 temp rise, then back to 200 where it sat. I kick it out and try again, it sits at 200 regen start a few, never goes to temp rise. So I take out the get the egt hot, I pull over at 600* and try the regen. It takes, EGT gets to 680* and it goes back to 200 regen start. wtf. What I need to know. What criteria must be met for each stage of regen, and what changes can kick it out? I don't want opinion. I need fact. If anyone out there is an Isuzu tech and has training info they would share with me it would be appreciated. I have IDSS and factory service info. I subbed for 3 days on Isuzu site and its the same info as on my scan tool, so that was a waste.

History, in the last year, its gotten NOx1 and 2, DPF, Last time it was here for a EGT temp sensor code, where the egr temp sensor broken off in the exhaust manifold. So it got a sensor and manifold. this last go around I did a DOC, EGT1/2, aftertreatment injector, so except for the SCR, the aftertreatment is all new. I did have a p0172 code set twice, which I cant prove out. data lists o2 content at 15% and 16% idling, I haven't watched it driving. And I noticed turbo boost desired is 15.2@idle and actual is 14.2@idle. And that's the only thing I don't like, Id like to see atmosphere at idle. But when it DOES go regen active, that value isn't any different.

Anyone out there have any ideas? Im out of ideas

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Matthew Mobile Technician
Bartlett, Illinois
Matthew Default
 

Does this one have the exhaust brake by the DPF? It is clear that you are not getting to temp for diesel dosing, I have tried driving the crap out of them and forcing a regen too, but if whatever gets the exhaust hot (VGT, throttle blade, etc.) isn't working it will not stay in regen. This is from an older Isuzu training manual: The exhaust brake valve is installed in front of the DPF…

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Jim Technician
Dover, New Jersey
Jim Default
 

Hmm, it is at 100% (open) and commanded as such. Do you have any training material explaining the different regen modes? And what has to happen during each one? What is baffling me is it can go active, then something happens and it goes back to start.

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Matthew Mobile Technician
Bartlett, Illinois
Matthew Default
 

Here you go.

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Jim Technician
Dover, New Jersey
Jim Default
 

Thanks but that's in service into. I mean like 20-warmup, 200-regen started, 220-temp rise, 370-regen active those modes. What requirements for each, what can kick each out. That kinda info. New info. It set a p0172 this afternoon. But once cleared it never came back. :shrug:

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Anthony Technical Support Specialist
Kirkwood, Pennsylvania
Anthony Default
 

Hi Jim: I'm by no means an expert. I don't have much in the way of answers or opinions. I have a bunch of questions though. Have you run the nozzle and SCR tests? Temps esnsors accurate? Got a Raytek? Are the NOx heaters working? Is the EGR working? Passages clear? Your EGT should get close to 1000, IIRC. Check for a cal update? I'm curious as to the motivation on changing the DOC. Unless…

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Jim Technician
Dover, New Jersey
Jim Default
 

I changed the doc, because in my experience, if the thing is dosing and not making fire, the doc is worn out. It does make fire now, but it doesn't always go into the regen. As I said above, it will sit at "200-regen start" forever, then sometime it will start the regen (370-regen active) then a couple times WHILE IN REGEN ACTIVE, will kick out into regen start. I see nothing changing when it…

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Anthony Technical Support Specialist
Kirkwood, Pennsylvania
Anthony Default
 

Hi Jim: As I think you know, the service information, TSBs, etc. is in the tool. It's been a couple of months now but I was involved with a 2016 or 17 NPR for aborting Regens. The procedure for diagnosing why is in the information. In our …e, we needed to run a couple of tests (after replacing one of the sensors and possibly (?) the injector). Then it would Regen. If it didn't pass the tests…

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James Mechanic
Hartford, Connecticut
James Default
 

I have a Isuzu with a very similar issue right now. Mine will never warm up enough to start regen. I was talking to a friend last night who works for Ryder and he said if it goes in and out of regen mode it needs injectors. He was quite sure of himself. I tried to compare two trucks I had here with the balancing rates and the one that warms up and goes into regen in four minutes had worse…

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Christopher Technician
Saskatoon, Saskatchewan
Christopher Default
   

Jim, I have a fair amount of experience on the 5.2L 4HK1 engines but only up to 2011, so not sure how relevant this info will be but this is how I would approach it... If your EGT 1 will not rise and be stable then need to isolate those systems that create the specific environment for EGT1 to rise.... I have in the past on extreme cases even removed the DPF from the chassis and initiated a…

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Jim Technician
Dover, New Jersey
Jim Default
 

I checked EGR flow. I don't know about the "glove test" but I did note the temperature of the valve, and it remained room temperature until commended open. The funny thing is the truck doesn't even go into temp rise. Like its waiting for something. But ECT is good and believable, IAT is good and believable, EGR inlet, EGT1 and 2 are all believable. Im stumped. I'll continue to pick at this thing…

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Jim Technician
Dover, New Jersey
Jim Default
 

Ok, I got it figured out. Regen wont continue because my LOAD is too low. Should be around 20% at idle. mines 0-2% at idle. If I turn on ac and lights etc and get load to about 6, regen will start and 220-temp rise mode will begin​.​As the compressor cycles and load goes below 5, regen kicks in and out. NOWWW the question is what input(s) are used to calculate load. None of the…

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James Mechanic
Hartford, Connecticut
James Default
 

FWIW, mine would not got hot enough to start regen. I had already replaced the exhaust brake a couple of weeks ago, but I did take the cover off and was able to adjust the stop so it would close a little tighter. After that I was able to heat up and start regen but now it keeps stopping after about 20 minutes with a "70 stop regen" pid. Then it will continue to start and stop regen on its own…

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Matthew Mobile Technician
Bartlett, Illinois
Matthew Default
   

Gotta love this, from Isuzu training... Engine Load This parameter displays the engine load in percent based on inputs to the ECM from various engine sensors. The scan tool will display a lower percentage when the engine is at idle with little or no load. The scan tool will display a higher percentage when the engine is running at high engine speed under a heavy load. Not very…

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Anthony Technical Support Specialist
Kirkwood, Pennsylvania
Anthony Default
 

Hi Jim: See id this helps. As I mentioned earlier, this should be in the service information in the tool. f01​.​justanswer​.​com/diesel3153/95d…​.​pdf HTH, Guido

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Jim Technician
Dover, New Jersey
Jim Default
 

Thanks for the reply. That table is to decide whether a normal or slow regen is necessary. That is in service information.

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Matthew Mobile Technician
Bartlett, Illinois
Matthew Default
 

Here is the training manual I have, maybe you can find something in there I missed. I would download it, just in case Scott has to pull it.

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Jim Technician
Dover, New Jersey
Jim Default
 

Thanks for the thoughts. Nothing I do seems to have any bearing on load. I can take CAC pipes off, put pipes on, open egr, close egr, remove the cooler, nothing seems to change load. What i did find weird is I have 2 trucks next to each other. Ones a 2012, ones a 2018. Should be close enough. The 2018, with egr at 40% Im at 26gps, 16% load. The 2012 Im at 30gps, egr 22% but load is 1%. If I take…

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Matthew Mobile Technician
Bartlett, Illinois
Matthew Default
 

There is a little bit of aftertreatment added at the end. Unfortunately that is the latest training manual available for purchase right now :(

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Mike Owner/Technician
West Palm Beach, Florida
Mike Default
 

What happens if you put the truck in gear, apply the emergency brake and chock the wheels? Does that raise the engine load? I don't know if these will perform a forced regen while in gear. I have done many forced regens on these trucks, but never tried in gear. The biggest struggle I have had with forced regens on these is getting them hot enough to start. If the truck hasn't just been driven…

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Jim Technician
Dover, New Jersey
Jim Default
 

They wont regen in gear. If i turned all accessories on, including ac, it regened. But kicked out as the compressor disengaged. Then went back into regen as compressor went on again. I wound up replacing the differential pressure sensor because despite it looking ok in idss, on my autel it looked weird. I didnt know which values to trust so i swung it. Seems to have worked. Regened for me a…

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