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Discussion Starter · #1 · (Edited)
Just recovered from a pretty jarring cross-country trip with my '16 Baby Duramax. Wanted to put the story out there in case it helps to save any other cross-country travelers from the stress of a high level pucker factor while you're on the road. Apologies for the length of the post, there's just a lot of things to recount. If you need a tl;dr, jump to the end and understand there may be some context you'll miss out on.


Early October I travelled east to west on I-40, towing an empty 6x14 tandem axle cargo trailer. I kept my truck in Tow/Haul mode for most of it, especially going through the mountains in Tennessee and the hills through Arkansas. I was running 70mph for the early portion of the trip, which in tow/haul, meant I was running at about 2200rpm. For reference, in regular driving mode, it'll drop into 6th gear and I'll run at 70mph at around 1700rpm.

Right around the New Mexico/Texas border, a message popped up "Exhaust Fluid Quality Poor", along with the countdown to limp mode. For reference, the full countdown to limp mode looks like:
  • 100mi until max speed reduced to 65mph
  • 100mi until max speed reduced to 55mph
  • 75mi until max speed reduced to 4mph
Being naive and trusting the message, I assumed I put in some bad DEF and started adding better DEF fluid (see #1 below for the video that helped me here) at each fill-up to try and dilute the DEF tank per the owner's manual. Eventually the message cleared and it seemed like I had sorted things out and kept on moving. Some quantity of miles down the road, the message came back, but the countdown timer had continued counting down instead of resetting, so now I was about to be limited to 55mph, with the nearest Chevrolet dealership approx. 120mi away. I got a call back from one of the service writers who, thankfully, actually seems to have some in-depth knowledge about how the truck works. The first thing she asked me when I explained what had happened so far: "Are you towing a trailer?" In our back and forth, I come to find out they see a surprising number of people with my exact situation popping up when they start crossing through New Mexico. What I was told is that while towing or under that kind of load, DPF regen will not happen. The only recommendation GM has for a customer to try and fix, is to unhitch from the trailer and drive on the highway unencumbered for ~40mi in hopes that it will allow DPF regen to happen, "hope" being the keyword.

I'm an engineer by trade, and a nerd by default, so I've got more tools than the average owner that surface knobs on different systems of the truck that aren't made visible to customers. In my case, the tool I poked around with is a FlashScan from EFILive (~$1000). I think you can surface the same Scan and Test functionality with one of the Autel MaxiSys tools for several hundred dollars cheaper (and without needing a laptop). Recognizing I wouldn't be able to limp to the dealership, I started digging into questions with the service writer about exactly what they were going to do at the dealership to get this cleared. Fortunately, she was really helpful with calling out some of the tests they'd have to run. She didn't know all the tests off the top of her head, but enough to help me narrow down what I needed to look up.

Along with a bunch of other bits and pieces scattered around the internet, I found a couple GM Tech articles and a Diagnostic Tip (all linked below in #2) about debugging the SCR (Selective Catalyst Reduction) systems on the larger Duramax engines. These helped to better understand what might be triggering the messages, and the test procedures that could help clear it. With the FlashScan, I was able to run a SCR Service Bay Test, and I was able to run a Diesel Reductant Quality Test/Diesel Exhaust Fluid Quality Test. Running the SCR Test first, and then the Reductant quality test second, is what seemed to rectify the situation. Just one or the other wasn't enough to clear the error - they had to be run in sequence.

The important thing to note here is that I was figuring this out on the fly, first on a desert exit off the highway, and then again in the parking lot at a hotel. I annoyed the other guests with the service bay regen in the evening - it didn't clear the message. I called it for the night to eat, rest, do more research to figure out next steps, and then the next morning, I ran the reductant quality test and that cleared the error. Later on in the trip I had to do the same procedure again, but this time with 5 minute gap between the tests that didn't clear the message right away - the message cleared on its own after getting back on the road to go as far as I could and just get to the next hotel. So, there's some period of "ignition off" time between the two tests that needs to happen, but I'm not sure exactly how much.

I've got the technical stuff distilled below as best I can. If you made it this far, thanks for reading and sorry I couldn't be more concise. Hope this helps somebody else avoid what I went through.

  1. How to read the expiration on DEF fluid:
    • Most manufacturers print the manufacture date using the Julian calendar format, because driving 10 hours a day heightens your mental awareness and they know you need a puzzle to solve so you don't get bored at the fueling station. Not hard to decode it, but not obvious if you're not familiar with it, so figured I'd link this here.
  2. GM Tech articles that helped me out
  3. Test Procedure to verify whether SCR components are working as intended (and hopefully clear the "Exhaust Fluid Quality Poor" message)
    1. Run SCR Service Bay Regen
      1. The engine idles up to ~2000 rpm, before increasing to ~2500rpm. From here, the engine and fan will pulse and make a ton of noise. I thought I was going to break something. In my case, it ran for ~20-30m - some documentation I've come across said it can run for upwards of 60-75m. You'll know it's finished because the truck will go back to a normal idle.
      2. Make sure the hood is up for cooling. The first time I left the hood down, and apparently the coolant hose swelled so much that it locked the clip, so when it cooled down, the hose shrank but the clip was stuck at max position and then the coolant hose just popped off the reservoir and created a grand ole mess in the engine compartment.
    2. Turn off the ignition for some period of time.
    3. Run Reductant Fluid Quality Test
      1. The engine idles at ~1900rpm. In my case, the test took about 20-30m. Similar to the Service Bay Regen, some documentation I found said this could run upwards of 60m. You'll know it's finished because the truck will go back to a normal idle.

EDITED FOR NOTE ABOUT "EXHAUST FLUID QUALITY POOR" MESSAGE
I think it's important to note that this message really doesn't speak just for the exhaust fluid. What it actually means is that the NOX2 sensor is reading pollutant values which are not within the threshold of the values read at the NOX1 sensor. NOX2 expects some threshold of pollutants less than what are being read at NOX1, and if this threshold is exceeded, this message can get triggered. This condition can be caused by faulty NOX sensors, bad exhaust fluid, a clogged DPF (Diesel Particulate Filter) or other faults in the emissions system that might cause the exhaust to be more polluted than normal. Just something to keep in mind if you're trying to debug this condition on your own. It's a pretty large scope of potential problems.
 

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Glad you got it sorted out! Just a heads up, regen is not for the SCR so any SCR/DEF related messages or issues won't be related to the DPF or DPF regen. The regen process takes place downstream of the SCR. The DEF tests are definitely good to know about and be able to trigger to try and clear up issues with bad DEF or at least hopefully reset the countdown.

Sent from my SM-G986U using Tapatalk
 
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Diesels used to be simple creatures that were easy to work on and ran forever. Encumbered with all of this emissions crap, they’re finicky and over complicated.
 

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Discussion Starter · #4 ·
Glad you got it sorted out! Just a heads up, regen is not for the SCR so any SCR/DEF related messages or issues won't be related to the DPF or DPF regen. The DEF tests are definitely good to know about and be able to trigger to try and clear up issues with bad DEF or at least hopefully reset the countdown.

Sent from my SM-G986U using Tapatalk
Thanks for bringing up that clarification. I think one of the other points here is the terminology being used in the software. EFILive DVT Controls called this a "SCR Service Bay Regen" or something like that, but the functionality of that test lined up with the descriptions I found of what a DPF Regen test would look like. So yeah, this is a good callout. Hopefully anybody else using a different tool will have it more clearly labeled in their tool's software.
 

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Something similar happened to me once, however, I wasn’t towing. I was about halfway through a 1500mi trip driving from CA to TX when I got the same “Poor DEF quality” message and subsequent count down to speed limited. Luckily for me dumping in a fresh gallon of DEF cleared the message and count down and neither came back. I definitely would not have been able to take the steps you did. Thanks for the insight and info.
 

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Thanks for bringing up that clarification. I think one of the other points here is the terminology being used in the software. EFILive DVT Controls called this a "SCR Service Bay Regen" or something like that, but the functionality of that test lined up with the descriptions I found of what a DPF Regen test would look like. So yeah, this is a good callout. Hopefully anybody else using a different tool will have it more clearly labeled in their tool's software.
Service Bay Test*
 

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Another reason this will be my last diesel... Thanks for all of the info.
 
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Another reason this will be my last diesel... Thanks for all of the info.
I got rid of mine years ago. All gas for me.

I know that’s hypocritical considering I made Gretio. But software can only go so far. At some point parts will be gone, and no one will make them. We’re having enough problems getting NOx sensors.
 

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I have used my truck to tow light to moderate loads (<5K#) thousands of miles all across the country. I've never had this problem while towing. I rarely use the tow/haul mode, generally don't need it. Maybe that's the difference?

And, I have never towed through NM, either. ;)
 

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@thewams By any chance was the bad DEF you added "Peak Platinum"? The Platinum is key and if it was Peak Platinum then that actually makes sense because that DEF has been known to cause a lot of problems for a lot of people, either because the formula doesn't actually meet API requirements or because it expires on the shelf because the price is absurd as there's no reason to have "Platinum" DEF since DEF is a very specific formula and Peak is just trying to rip people off.

For everyone else in this thread being overly dramatic, please... The OP's situation is one very few people end up in compared to the total number of owners of these engines. If "this is your last <insert product here>" were the case for any product that didn't have a 100% reliability record then you'd be walking barefoot everywhere. Nothing is perfect and expecting perfection is unrealistic. Expecting the worst to be the case for the majority of owners is also unrealistic.

Maybe GM should warn people about the 8-speed issues in their ads, or Ford should warn people about cam phaser issues in their ads, or Chrysler should warn people about the HEMI tick in their ads, or...

Come on.
 

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Man I have been using 3 year old cases of Oreilly's DEF and haven't seen an issue like this yet.
If I kept DEF in my basement storage room I bet it would last quite a while, between the cool temps and no sunlight it should last a long time. Actually, if DEF is stored out of direct sunlight at a temperature that never exceeds 50F then it will have a shelf life of 3 years. Sunlight and warm temps kill DEF shelf life.
 
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I guess that might be a reason to not completely fill your def tank in the summer, unless going on a long trip towing. My garage can get pretty warm.
Shelf life is based on average daily temperature for the entire period the DEF is stored and not maximum temperature. The snippet from this doc explains it pretty well.

Rectangle Font Parallel Screenshot Number
 
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If I kept DEF in my basement storage room I bet it would last quite a while, between the cool temps and no sunlight it should last a long time. Actually, if DEF is stored out of direct sunlight at a temperature that never exceeds 50F then it will have a shelf life of 3 years. Sunlight and warm temps kill DEF shelf life.
Mine is stored in a detached garage that is not air conditioned, so it does regularly exceed 50F in there but it also sits on the concrete floor out of sunlight and so I would guess it probably maintains a fairly low temperature even during the hot summer days.
 

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Before I comment, I want to clarify I have no interest in starting another gas vs diesel flame war. I like both the Otto and Diesel cycles just fine, thank you.

But this isn’t a one off issue. I’ve read numerous issues with the Colorado/Canyon Diesel engines on this board just like I’ve seen numerous 8 speed issues addressed on this board. At some point you have to face facts and accept that there is in fact a reliability issue with the 2.8. Shouldn’t be a surprise to anyone since it’s an Italian engine.

I’ve seen a lot of you diesel guys have found solutions to deal with the various reliability issues and that’s great. The 8 speed guys have too. But ultimately you are having to work around, dr up, jury rig, or over maintenance around the problem. So let’s just call it what it is…a less than stellar engine in the reliability department. There’s no need to keep polishing this turd.💩
I never said it was a one-off issue. Yes, others have had similar issues before but they are in the vast minority of owners. Which is my point. No vehicle is perfect, go to ANY vehicle forum and tell me which vehicle is perfect so we can all buy it. You won't find one. But you'll find people that will dramatically state "this is my last <product>" in someone else's thread about an issue.

You must also realize the emissions system IS NOT part of the engine. It wasn't designed or manufactured by the engine designer. Saying these emissions issues are because the engine is based on an Italian engine is hyperbole. Judging an entire vehicle or powertrain based on trouble posts on internet forums is simply ridiculous. Again, if we all did that then we'd never buy anything. The forums are full of complaints. Why? People seek out forums to either complain, to find fixes to problems, to talk about mods, or to get some input before buying. People don't come to forums to spread the word of joy or say "Hey, just wanted to let you know I've had another week where everything was great!"

To say "there is a reliability issue with the 2.8" is, again, hyperbole. One could say "everyone is sick" if all they did was hang out in a hospital all day.

I'm not denying there are people that have had problems. EVERY vehicle has problems. Some more than others, sure, but to sit here and see NON-OWNERS think they know better than owners is laughable.

There aren't reliability issues with the 2.8. There have been random issues and some problems early on, but the vast majority of these trucks have been problem-free. You just don't hear about them because the owners don't post up saying as such.

Now, you want inherent reliability issues then let's talk about the Ford 6.0 PSD. The LB7 Duramax. The Bosch CP4.2 HPFPs. The 3.5 EcoBoost cam phasers and associated recall. The Subaru head gaskets. The Toyota frames. You get the picture. The 2.8 has never been so unreliable that it has become notorious like some other vehicles or engines. Condemning the 2.8 as "unreliable" based on some forum posts is just nonsense. Enjoy your V6 and 8-speed. I hope it serves you well, but just parroting what other people have said about a vehicle you don't own does nobody any good and just adds to the drama.

If the 2.8 were as bad as you think it is then I guarantee you none of us would still own them or be willing to buy one again. Not making excuses. Not jury rigging anything. Not over-maintaining anything. "But YoU ARe UsINg a CatCH CaN!" - Yeah, and not using a catch can isn't going to cause some kind of failure. Catch cans also aren't specific to diesels.

I just get tired of non-diesel-owners coming along and trying to tell owners the "real facts." Get off it already. I've owned diesels for over 20 years and currently have 2 parked in the garage. But by all means, continue to tell us the "real facts" because we're just too blind to accept reality. :rolleyes:
 

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Before I comment, I want to clarify I have no interest in starting another gas vs diesel flame war. I like both the Otto and Diesel cycles just fine, thank you.

But this isn’t a one off issue. I’ve read numerous issues with the Colorado/Canyon Diesel engines on this board just like I’ve seen numerous 8 speed issues addressed on this board. At some point you have to face facts and accept that there is in fact a reliability issue with the 2.8. Shouldn’t be a surprise to anyone since it’s an Italian engine.

I’ve seen a lot of you diesel guys have found solutions to deal with the various reliability issues and that’s great. The 8 speed guys have too. But ultimately you are having to work around, dr up, jury rig, or over maintenance around the problem. So let’s just call it what it is…a less than stellar engine in the reliability department. There’s no need to keep polishing this turd.💩
Idk, I keep seeing a few threads with alleged reliability issues, some of which end up being owner induced, but I can still count the legitimate complaints on both hands. And that isn't anywhere near the number of 8-speed complaints from people who can't spell shudder. Meanwhile in real life I haven't experienced any reliability issues with my 2.8
 

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If the 2.8 were as bad as you think it is then I guarantee you none of us would still own them or be willing to buy one again.
I don’t know, people still buy Land Rovers. 😂

I don’t want to give the impression that I think the 2.8 has reached Pinto levels of unreliability, but it’s up there with the 8 speed shutter. That’s a high enough level of concern to at least give a prospective owner pause before purchase, as the 8 speed issues did for me before I pulled the trigger and bought one.

Again, I really like Diesel engines, but all of these emissions related issues, injectors burning holes through pistons…that’s more risk than I’d be willing to take.

But I respect your opinion on the matter, as you seem to be one of the most knowledgeable 2.8 owners on the site. And you’re right that other engine architectures have issues too. I’m all too familiar with the Pentastar 3.6’s flaws.
 

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Discussion Starter · #19 ·
@thewams By any chance was the bad DEF you added "Peak Platinum"? The Platinum is key and if it was Peak Platinum then that actually makes sense because that DEF has been known to cause a lot of problems for a lot of people, either because the formula doesn't actually meet API requirements or because it expires on the shelf because the price is absurd as there's no reason to have "Platinum" DEF since DEF is a very specific formula and Peak is just trying to rip people off.

For everyone else in this thread being overly dramatic, please... The OP's situation is one very few people end up in compared to the total number of owners of these engines. If "this is your last <insert product here>" were the case for any product that didn't have a 100% reliability record then you'd be walking barefoot everywhere. Nothing is perfect and expecting perfection is unrealistic. Expecting the worst to be the case for the majority of owners is also unrealistic.

Maybe GM should warn people about the 8-speed issues in their ads, or Ford should warn people about cam phaser issues in their ads, or Chrysler should warn people about the HEMI tick in their ads, or...

Come on.
My first thought at the time, was the last jug of DEF fluid I used which was the generic stuff you can get at Flying J. My thought process around it was, naively, how complicated can sheep piss be?

I remember that bottle had some dust on it - may very well have been a jug gone bad. I wasn't checking for manufacturer dates or any of that stuff. Ultimately a good lesson learned. All said, while I'm doing the post-mortem on all this, I'm not certain if these were actually two separate problems, or if it was all down to the soot accumulation on the DPF due to the lack of the regen. From what I've read, the text on the message is very specific, but the actual trigger for the message is pretty ambiguous. Something else that was part of the process of whittling down to a workaround and helping me narrow down the cause: there were no DTC's. The reason I mention this is because there are specific codes for a failing NOX sensor, and for faulty DPF injector. None of that is gospel, but it did help me operate from a stance of "okay, the actual parts seem to be in working order - what else is there to look at". Unfortunately the only way I could prove/disprove the fluid quality with any certainty to run a test with a specialized tool. I think it's the J26568.
 

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I don’t want to give the impression that I think the 2.8 has reached Pinto levels of unreliability, but it’s up there with the 8 speed shutter.
I'm not sure what you're basing that on, but it's clearly not the number of posts here on this site. Those were incredibly common when I first joined this site.
 
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