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Jeremy, Certified Truck/Bus Technician
Category: Medium and Heavy Trucks
Satisfied Customers: 3382
Experience:  ASE Med/HD Truck Technician, NATEF Diesel Engines and Electrical/Electronics Technician, EPA 608/609 HVAC Certified, Steering/Suspension and ABS/Brakes Technician
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2011 Isuzu NPR with 3.0 ecodiesel DPF runs every 30 miles. I

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2011 Isuzu NPR with 3.0 ecodiesel DPF runs every 30 miles. I have had DPF backed and cleaned and tested, it passed. Replaced knock sensors a few months ago testing good, replace differential pressure sensor had a code, know code is gone, replace screen to dpf at tank was dirty and kinda plugged. Check injector flow at -.02 to .02 good. replaced air filter, cleaned intake manifold, without removal, and checked and cleaned egr valve not very dirty at all. Cleared all engine codes did reset on all in computer and DPF. I have no codes at all now. Still regen every 30 miles. Check def injector spray pattern, and for leaking. I had no brake out box to do volume. Could a DEF injector cause the system to go into regen to often, I OHM tested at 13 OHM, Good. Remember 3.0 has only 1 Injector. DEF Injector. Please what am I missing?

My name is ***** ***** I will assist you with your question today.

I'm an independent contractor and I don't get paid until a rating has been made.

We can go back and forth as needed to help resolve the issue you are having. Follow ups are free after ratings, so rate in confidence!

Yes, I am familiar with the system having only 1 injector. It can cause the need for more regens if the NOx sensor aka bank 1 sensor is reading wrong. Same as if the pdf pressure tubes are blocked. That sensor being bad can cause it.

Another problem that can cause it is a turbo going bad. Do you have the ability to start the regen and monitor the pressures of the turbo boost and the temps of the regen system? If so, activate the regen and see if you are building first at above 1400 degrees, than above 1800 degrees. That is the lowest threshold for the temps. If you are not getting that, then the turbo is not sending down enough pressure to get the temps up.

What codes did you have before? Also, do you have the VIN so I can pull the checklist off IDSS and get it sent to you?


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Customer: replied 4 months ago.
Customer: replied 4 months ago.
Customer: replied 4 months ago.
Customer: replied 4 months ago.
Customer: replied 4 months ago.
Can a injector for the def to the catalyst cause this if under or over spraying. could you tell me with one under or over?
Customer: replied 4 months ago.
Good Morning, I hope you are in today. The customer took the truck for a few days. I have it back.
Customer: replied 3 months ago.
I will rate you and tip, sorry the truck was picked up and then returned. Please help

I apologize. I was off for a few days due to being sick with "Acute Pneumonia" aka a super bug. Still trying to recover from it.

The NOx sensor is the oxygen 2 sensor. It is the sensor at the SCR inlet.

The boost sensor is on the intake after the turbo.

Yes, the DEF injector aka diffuser can cause issues. So can a harness and a DEF buildup in the system.

Do you have the codes that you are getting and I can get the troubleshoot charts for them.

Customer: replied 3 months ago.
The bank 1 nox is reading good , what is the information I am looking for.
I have the IDSS, What boost pressure do i want to read at regen. I am building temps of 1100-1200.not 1400-1800. At one time i had dps code replaced and cleand tubes, then it went away. I also have had p2000. I have done the test bu the book. Except injector volume. I don't have a brake out box, for this test.
I was told by a frind at Isuzu that the def injector is a problem with this isue, is this true
Customer: replied 3 months ago.
PS hope you are well soon!
Customer: replied 3 months ago.
is it nox sensor 1 or 2 and you are saying nox sensor and o2 sensor are another unit right what are you needing me to know on this?

Sounds like the DEF injector or metering valve may be acting up...

NOx Sensor Inlet is the O2 number 2 sensor. They are the same exact sensor. O2 sensor 1 is the one that is before the dpf filter. Then you have the NOx outlet sensor.

If you are getting up to 1200, are you above 601 on the inlet? If so, you should be passing. I like to see 1400 myself with a max of 1800 and around 800 max on the inlet. If you are barely above the 601, then there is a doser issue for the pre warm or an issue with the metering.

Customer: replied 3 months ago.
Well changed def injector, he didn't do an at rest reset. Will this effect the outcome? Drove it got up to 55. better, but just a few miles befor lite up dash red exhaust, small yellow at right regen. code P2000, and code P209C. diff press sensor at 80 kpa, boost desired and demand good 14.9 , regulator 48-50 %, at 1000 rpm cyl 1 -.1, cyl 2 -.8, cyl 3 +1., +.4, is this all good? mass air 11., Please tell me anything I need to monitor. Remember 3.0 eco model.

All those look good.

Do the maintenance reset on it in the regen section/dpf filter and it should calibrate the pressure sensor, then the code shouldn't come back.

Customer: replied 3 months ago.
Can you tell me step by step how please
Customer: replied 3 months ago.
What is considered an average for this engine on this show me a 14 foot box truck with a 3.0 liter regen how often how many miles considered average especially on a mix city/highway kind of give me at least an average if you could please thanks
Customer: replied 3 months ago.
It has 148k and dpf has been baked
Customer: replied 3 months ago.
can catalyst side cause more dpf regen?

You have IDSS. The instructions for the maintenance reset is in the program.

No, the SCR side won't cause more regen, It will cause more DEF fluid to be used. Now the Catalyst on the regen will cause more dpf regens if there is still a fault, like a bad turbo.

Customer: replied 3 months ago.
I have had to teach myself how to use computer. Where can i find maintanance reset
Customer: replied 3 months ago.
Still no miles average regen?

If you are using a Pro license, you click the scan tool, it opens up and then you click the live data. You will have the tabs at the top for engine, EGR, CMP actuator, fuel trim, etc.

Select the customer field and then you get the box to add the fetures to monitor. Add the dpf outlet pressure and the inlet, then the aftertreatment status. After that is added to the box on the right, you then select add at the bottom and it returns to the live data. Go to the custom that just created and then you can scroll down to the status. Click it and inside it give a box that shows maintenance reset. You then click it and it resets the filter.

The other way to do it is through the controller programming. You open that one up, click the sensors list at the top, select PGN then select aftertreatment. Select the continue box at the bottom then you can select the maintenance rest and the server will reset the filter in the ECM and reset all the parameters in the vehicle. Once that is done, select the "send to vehicle" box at the bottom and then it will have a box on a couple minutes when t is done. Then you an start the truck and go again.

On the miles for regen needed, that varies by truck, outside temps, air quality, idling, stop and go traffic, etc. On average it should go about 300 miles before a regen will be done in passive meaning the truck will do the regen when driving. Otherwise it will need assisted (pushing the button after parking) if the truck isn't on the road for 20 min above 40 mph when the regen light comes on.

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Customer: replied 3 months ago.
we decided to adjust the valves. This was the only thing that worked. Evan after replacing dpf.
Customer: replied 3 months ago.
I didn't see anywhere in the book.