Thank you for the great explanation This has helped a lot they need to come up with an update fix with a lower parameter.

Thanks, dude. I'm new to disel and I work by myself in a new shop. This video helps out a lot.

So, ture maintaining a fleet of 20 M2, I have done a lot of roadside called just cause of the code. 😮‍💨 great job explaining it.

This is the real world fix and is 100 percent correct. Keep them trucks running brother.

I really have trust issues, but you seem like someone I would trust with my big baby. Giving out great info just to help us out. You are a blessing. Next time I'm in Florida, I'll reach out to you about possibly doing my valve lash adjustment. Coming up on 500k miles on my DD13. And if I haven't bought the datalink yet, you can do the scr tests also.

Fantastic video very well explained. Easy to understand if you have worked on dd engines after treatment 👌

What a great help brother!! If you were here I would give you a hug!! Keep up the good work !! Thank you!! 🦾

There is an ACM update that helps reduce that fault. It’s software level 7.61.1.0. All other power train modules will have to be updated as well to avoid configuration errors. With the after-treatment cold, check Nox sensor dew point hours under Actions->Aftertreatment->Nox sensor verification tab. Wait for dew point hours to populate (takes a couple seconds) if either sensor is over 8,000 hours, it’s a good idea to replace both of them. Great explanation. I hope my add on will help others

Thanks, I’ve been going crazy on this code!!

Very helpful video, Thanks

Thank you for sharing this very helpful content

Thanks for the info you save me

LARMF stands for lumped average of magnitude frequency, it’s an algorithm the acm uses by sampling frequencies to adjust def quantity dozed into scr to prevent ammonia slip. I have found several times that if you perform a def quantity test 3 times on the second or third time it will fail. Majority of the common failures happened on units with a poor duty cycle who travel through local city traffic with light loads, I always tell repeat failures to adjust routes to allow for longer drives and dog the truck when you can to help burn off soot loads

Thank you for uploading this video. I got the same issue, Both fault codes (520372-16 and 520371-16) popped up about 4600 miles after the DEP cleaning job (baked). I was going to take it back to the shop buy find your video and read all the comments. The following is what i did: 1, Run Nox sensor verification first. the result: pass. 2, Perform Parked SCR Efficiency Test, This test took about 2 hrs. I didn't finish this test, because the software was not responding at some point. I restart the program and ran it again (but I didn't finish the test, don't know what the end result looks like). The ASl: NH3 LARMF compensation factor value went from 0.74475 to 0.92993. Both fault codes went away when the value got to 0.92993. While it was running the Parked SCR Efficiency Test, both SCR Inlet Nox sensor and Outlet Nox sensor readings are around 380ppm and 0ppm ( I did see some -1,-2-3). the Nox conversion efficiency value is almost always at 1.0000. These are really weird fault codes. I just want to share my experience with others, I hope it will help others. As you said in the video, they will come back, Let's wait and see how soon it will come back, I will report back. Thanks! Be safe everyone.

2 trucks came in today with the same issue. Your video helped alot. You should only need to do the scr once though. Did you check to see if the doser or the hole the doser goes into is plugged? Thats what happened to both trucks which messes with how the scr efficiency is calculated. I cleaned out both, ran a Def quantity test to make sure the doser was spraying afterwards. Then I did the scr test once on both trucks. The code went from active to permanent. At that point you wanna reprogram the ACM and the code will be completely gone.

Software updates for the ACM allegedly are supposed to be tweaked to make this issue less of a problem.

Thank you ,the truck shut off red warning light at 0.925.

I have this same issue I have replaced sensors filters and it's driving me insane looking at those lights. So far I've logged 2 thousand miles and no derate I clear code it comes back 40 or so miles down road, some say pull outlet nox sensor and let it breath fresh air and secure it somewhere has anyone had luck with this, also repeatedly paying shop to clear via scr test and down time killing bottom line. Any hacks out there work for anyone. Other then delete don't wanna go that route but man they're forcing it with this b.s.

Good thing I bought the software. About to perform the 3rd round of scr efficiency tests in less than 5000 miles... why is the nh3 number dropping so fast.?

Information God bro

I work for a school district and do this every two to three weeks on two detroits we have . Has anyone been updated on a fix ? Im sure the constant idling waiting at the schools don't help either . Any one know any tricks ?

One time I had to cut the scr test short at about .93...the service light went off. I Said I would come back later to get the nh3# to 1.0.. about 300 miles later, i hooked it up to the computer to get the nh3 to 1 and it had gone up to 1 on its own

I am new to trucking and I would like to star diagnostic my own truck, right now my 2018 New style Cascadia has both 520372 16 and 520371 16 I had been lately idling my truck almost non stop, until today now that I got an APU, codes recently appeared in my dash, will this video help solve those 2 codes, also how do I get the Detroid Diagnostic Link ? And what type of cable do I connect to laptop to OBD port on truck? Thanks a lot in advance

Anyone got a new update from freightliner or a permanent fix? Same codes took to dealer charged $300.00 to tell me the same code i told them that displayed on dash. How many trucks with the same issue? There should be a campaign or recall for this issue. Going to let the Outlet Nox sensor breath fresh air like someone stated. I hope it works.

My SCR passed but when I did the Nox verification my Nox levels were not reading correctly. My inlet Nox was bad. All my softwares were up to date. Changed the inlet Nox and ran another Nox verification and the code went away and Nox levels passed.

How about an F-ing Class action lawsuit !!! Any attorneys out there?? I’m so sick of this emissions crap with Daimler Detroit Freightliner Inc. I don’t have the money to buy a new or even another truck or another One Box. How about some help for the workin slob for once?!?! ✌️ y’all.

Once the light comes on and the code comes back how long can you drive on it before it becomes a problem? When the truck does the auto regen while you're parked say on your 10-hour break does that bring the LARMF number up? I only ask because ever since winter time has come and I stop idling at night is when this problem started.. once the code is cleared it last anywhere from four days to a month before it will come back on

I have this code your explaining plus inlet nox high drift and erratic voltage for inlet nox

Any updates on a real fix? I hate to do scr efficiency test la they take for ever sometimes 6hrs + to get it to 1. And only lasts a month

So should I send this driver to the dealer since you guys are saying this is just a system update ? Or is there anything else I can do to get this driver back home? Anything specifically I should be lasering in on .

Thank you for the video. I have this code on a 2017 Cascadia. Would there be any benefit taking it into a shop, or should I keep clearing code with my diagnostic tool? Will excessive def use shorten the lifespan of one box? Should I load up my parts cannon and fire off at the aftertrement system? Thank you again

I'm Rachel Chavez sorry my daughter was logged in

I really wish that Detroit had implemented a function similar to Cummins' "Aftertreatment Maintenance - Reset All" feature. You still have to run the equivalent of the same tests with Cummins, but you wipe out the learned averages so you start with a clean slate and don't end up beating your head against the bricks repeatedly re-running the same test just to get a learned average above the minimum. So stupid.

Wondering if you might know why. But when I got the truck, I drove 7 months, almost 80k miles without this issue. Now that I'm running the scr efficiency tests, I have to run the test like every other week. Is there another test or regen I can do to prolong the time between?

Any updates ? My company has 54 2017 dd13 and closed loops everyday, we were told by dealer to chart all the nh3 bins and run repeated parked scr efficiency tests until all bins are @ 1.0 it's still only a temporary fix some trucks last 3 days some 3 weeks. I replaced the acm with one from a low milage roll over truck we had as a test still waiting for results

Will it come back again. My 2018 Cascadia has the same issue. Mechanic advised that the onebox needs to be replaced as the SCR efficiency is low. The other option he suggested is to keep the NoX outlet hanging outside. What's your take on this. Given the market scenario I am less inclined to replace the Onebox.

Should my temps run the same as a regen in the efficiency test?

I have a 2021 truck with same issue dealer will only do an efficiency test until MIL goes off and release the truck a week later lights come on..and so we go back and forth..is there a real fix for this issue?

I just bought the standard Version of diagnostic link 8. It made me run a dpf regen before running the scr test. The nh3 number comes up a lil but after 5 minutes the scr test stops. Am I doing this right? Just keep running scr tests? Correction. It was waiting for me to press the manual regen button. Scr system is stabilizing now. Wish me luck 🙏🏾

Hi I am having Same issue..its 2019 cascadia dd15. Both new nox sensors. Dpf clean.. def doser new..software updated.efficency stayed at .95 during tests..but after 4-5 hours driving code comes back again.spn 4364 fmi17,spn 520372 and 520371..plz shed some light

does this problem cause excessive def fluid consumption? And does consumption go back to normal after everything go back to normal. Thanks 😊

Question : I have OTR Performance device with app on the phone and I got and option for “Forced SCR efficiency regen” Is this gonna bring the nh3 value up ? Is it the same as SCR efficiency test you’re doing on the laptop ? Thank you

Take out the outlet nox sensor and drive. About 1000 miles No need to do SCR test. I’ll bring NH3 level to 100

How far back does this average go back to. Eng hr ?

Sounds like a ECM software problem.

What is software used for diagnostic here ? Thank u

Hello my truck has been in shop 3 times in 10 days with this code. Everytime they run scr efficiency tests and code goes away and they release unit. But it comes back again. They have changed nox censors. What else could be the problem.

So the $500 a year subscription will run scr efficiency test? And then you just need any laptop? Do you need internet while doing the test? Because it seems to me if I had the software to look at the code I would save money even with buying a laptop and paying $500 a month subscription... seeing how I've had the same problem as everybody else and I've replaced filters and the pump has been replaced and the nox sensors have been replaced.. where the light comes on as of now I'm pretty sure I know what it is but I'm not positive it could be something else so of course I have to bring it to the shop to get it looked at and then of course they want to run the tests again and they want to charge me at least this way I would know what it is and I can run the tests at my leisure.. they charged me $200 a pop so I figure after the 4th or 5th time will be clearing the code myself everything's already paid for itself and just like everybody else I get four days to about two and a half weeks before the code will come back on there's no telling

100%? maybe crystals of def in the decomp being dissolved by the heat and fresh spray of hot def causing over efficiency, there is no way the scr can be 1005 efficient

THANKYOU SIR it worked for me had the same code and the nox code.. Did the regen and scr efficiency test.. was arpund.71.. after 1 hour of scr testing went up to .93 and codes went away... Would the codes come back after how long ??? did a nox efficiency test eas at 98 percent.. I don't idle my truck at all have 400k only 2018 cascadia

What does it mean if that value won’t reach the .9 to 1.0 The highest it will go is .89014

Is there a yearly fee to keep datalink software? Are there any other softwares out there that will perform the same jobs?

Does the standard version of this software clear fault codes and reset derates. I have a 2019 cascadia.

Def injector (doser valve) is faulty your g/h of def should be between 500 and 800. Your DEF pump speed is too high shouldn't exceed 1200. Normal is 1100 - 1150 rpms. Your pump is working too hard because the Injector is stuck open. Need to look at ash percentage in the mcm and acm and also need to monitor the doc pressure. If it's getting up close to 1 or higher the dpfs need replaced.

Any fixes for the dreaded low nox efficiency code spn 4363 fmi 18.

I did that procedure and the engines truck ran away!!! It blew

How much you charge

What is best way to fix SCR system fault ?

code came back again

In order for me to deactivate this code by simply do force Regen 2 time and check nh3 1.00 the code would go away .

How long does the SCR TEST TAKE?

4364 fmi 17 keeps pop out.makes me 😢

Bro same problem on my truck please help?

So the real solution is to replace the one box.

Scr test means Regen?

yikes I just had these 2 codes come up... 520372 16 520371 16.. so no real fix. I'd don't idle at all.. so the real fix is not the dozer pump or the def filter.. so I need to get the data link software 🤔

I get the nh3 to 1.00 and the code is back later the same day. The only other code is 520349 14, which pops up first. Any suggestions?