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Duramax Fifth Generation: 2011-2016 (LML) Discuss the fifth generation (2011-2016) of the 6.6L Duramax diesel engine & associated components. Engine related discussion ONLY.

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Old 04-02-2017, 04:53 AM   #131 (permalink)
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Originally Posted by James Austen View Post
Hi All 'DEF Quality Poor' Experts, I am new to this forum and new to American truck ownership. I will say sorry in advanced as this is a rather long post.

I have a 2012 Silverado 2500HD with 33,000kms which has had a DEF Quality Poor Alarm and P20EE/P2BAD DTCs set for about 400kms now. I live in Launceston, Australia and the local GM dealership only does Aussie cars. I have not yet found a diesel mechanic that has an idea about these exhaust treatment systems or one that is even interested in learning. Its not all bad as I am a Robotics Engineer and deal with computer control of mechanical processes every day, so I purchased a Tech 2 to support my truck. So this is what I have done so far.

First I did what the manual says 'topped up the tank' and kept driving, of course this didn't fix it and for those of us that have now become friendly with our Mate 'DEF Quality Poor', this would probably be the last thing i would check. Now the rest is what i have done so far. I borrowed a diesel mechanics scan tool for a day, he was not interested in learning about these vehicles and fair enough too there isn't many in my town.

1. A DPF Service Regen, under instruction from the shop I purchased the truck.
2. A Reductant Fluid Quality Test (RFQT). No good
3. Power Cycle, ignition off, door/open close and wait 2mins.
4. A Second RFQT. No good.
5. Went for a drive. NOx 2 not going to 0ppm or following NOx 1.
6. NOx 2 readings did approach NOx1 after 10minutes of idling at 1500rpm with the Reductant Injector disconnected.
7. Ordered New NOx 2 sensor and purchased a Tech 2.
8. Installed New NOx 2 sensor, reset NOx 2 Sensor on Tech 2.
9. Went for several drives. The first drive the ECU wanted to do a DPF regen so I drove until it completed, it completed at 6g of soot. The second and third drives, No Luck still have the DEF Poor Alarm and P20EE. P2BAD was now gone from confirmed and pending DTCs, but still in permanent. During these Drives I did multiple hard acceleration/ coast Deceleration, both NOx sensors went to 0 ppm. Yay thats something different.
10. Performed a RFQT and recorded NOx and EGT values every 2 mins. Test Timed Out, Ave NOx1 -136ppm, Ave NOx2 - 13ppm. Cooling fan ran flat out all test.
11. Performed second RFQT. Timed Out. Ave NOx1 - 118ppm, Ave NOx 2 - 11ppm. Cooling fan Stopped half way through test.
12. Reductant Injector Leak Test, passed no leaks.
13. Reductant Injector Spray test, 3 nice jets atomising well.
14. Reductant Injector Volume Test, 3 tests done averaged 17ml in 60secs.
15. Reset NOx2 Sensor and NOx Catalyst Loading.
16. Performed Service Regen, Completed Successfully. Aves were, NOx1-140pp, NOx2-152ppm, EGT1 - 341 C, EGT2 - 584 C, EGT3 - 579 C, EGT4 - 557 C.
17. Went for a drive around the suburbs for 25mins.
18. Into another RQFT without turning truck off, This time when it timed out the Tech 2 actually beeped and said activation timer expired. Aves were, NOx1 - 136ppm, NOx 2 - 11ppm, EGT1 - 280 C, EGT2 - 294 C, EGT3 - 280 C, EGT 4 - 260 C.
19. Power Cycle all systems > 2mins.
20. Another RQFT, result as for 18. Aves were, NOx1 - 137ppm, NOx2 - 17ppm, EGT1 -281 C, EGT2 - 294 C, EGT3 - 280 C, EGT4 - 265 C.
21. Power Cycle all systems > 2mins.
22. Another RQFT, at the 57minute mark I interrupted the test, it was just the same as all the others.
So in all this there are 2 things that I have not confirmed, 1. that the 9th injector is not leaking and 2. that there is not a minor exhaust leak.I dont see how these would be interacting in this, but please correct me if i am wrong here.
Now on to the DTCs, at no time during any of testing from point 10 onwards has a DTC set, in fact i now have no confirmed,pending or permanent DTCs. So during my testing the ECU has obviously decided that P20EE and P2BAD no longer exist, but it still thinks I have poor quality DEF ? How can i have poor quality DEF if the NOx catalyst Efficiency is ok ?

So I need some advice on the next step because I believe I have an SCR system that is working as it is reducing NOx by more than 70%, in fact it appears better than 90%, yet the ECU will not acknowledge this and pass the RQFT.

I don't believe this truck has the latest calibrations in it, but still need to confirm this.

G'day James, I've been through this too. Please feel free to call me on 0414890148 and I will let you know how I got my Chevy running properly for once and for all.

Bill Roach
Kadina, SA

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Old 04-04-2017, 07:57 AM   #132 (permalink)
James Austen
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Join Date: Apr 2017
Location: Tasmania, Australia
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G'day Roachie, thanks for the reply. I will do in the next few days.


2012 Silverado 2500HD , LTZ
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Old 05-08-2017, 02:26 PM   #133 (permalink)
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Location: Woodland, CA
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So is this still an issue with the newer trucks? Like the 2015's?
2019 GMC Sierra 3500 SLT Dually Dmax 4x4
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