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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 01-13-2019, 04:02 PM   #21 (permalink)
Ted White
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At the start of the regen cycle fuel is injected through the 9th injector in to the exhaust stream (or through the engine injectors pre 2011) to raise the temperature of the DPF, so regen is active during this phase.

Once the DPF reaches flash point temperature for the carbon (soot), it starts to burn off by itself, using oxygen released from the exhaust by the DOC. The system monitors progress and temperature and will start injecting fuel from time to time to maintain the temperature - regen active.

Also, the regen temperature is not held constant, it cycles up and down in a controlled manner, which requires the injection of fuel to go off and on from time to time. It's a complex program, not a simple burn.

On DEF equipped vehicles, DEF is injected to help cool the SCR and DPF at the end of the cycle.

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Old 01-14-2019, 12:25 AM   #22 (permalink)
Dmax Dually
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Ok so when I parked my truck at work it just finished a region and my soot level was 0. When I got back in my truck after work and started it the soot level was 11g. Everything was normal and my miles since last region was reading 3 which was about right. After about 5-10 mins of local driving my soot level was 17g. Then at a stop light I noticed the truck kicked in to high idle 800 RPM ( normal idle is around 630-650) which is telling me the truck is preheating for a regen. Then about 2 mins later the DPF stat showed 'ON" for a few mins and my post DPF egt #4 showed about 900+ and my soot level was still 17g. About a min later the stat switched off and my soot was about 12g. The truck stayed at high idle for several more mins. Then it dropped back to normal (650 rpms) for the rest of the drive home and soot level was at 17g. Why would the truck go into regen with a soot level of 17g right after it just completed one?
Over the past several months before I got my CTS I alway thought my truck was regenerating way too often by the high idles all the time but I never had any codes. I'm thinking the DPF differential pressure sensor might be bad. I might just change it out and check the lines..

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Old 01-14-2019, 09:34 AM   #23 (permalink)
Ted White
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You can lose a lot of sleep trying to work out what is going on during a regen. I've watched dozens and dozens of them and there's no guaranteed pattern, but I can say that there's nothing worrisome about what you've described Dmax Dually. The soot load is measured using the pressure differential across the DPF so it is nowhere near accurate. There isn't any direct "weighing" of the soot, it's all just a guestimate. The regen cycle will run and restart according to the preset programming, and is not just dependent on soot load.
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Old 01-14-2019, 10:37 AM   #24 (permalink)
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Ted..Thanks for the info and your experience. Yeah..I'm going to leave it alone. I've been lucky my truck runs great and has been since the day I got it. The few small issues I had like glow plugs, coolant recovery tank cracked, steering gear replaced, etc have all been taken care of under warranty. Knock on wood, I haven't had any major issues and I have never been stranded or in limp mode.
I've just finished all the mods I plan on doing to it over the past month. The eng is completely stock. I installed a MaxTow triple gauge A-pillar pod, a Fass lift pump, Edge evolution CTS 2, Amp's throttle booster and last but not least a Banks cold/ram air intake with a super scoop. It's like a different truck and the dead pedal is gone...
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Old 01-21-2019, 10:20 AM   #25 (permalink)
jerkyboy
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I agree with a lot of what's been said about reading too much into the regen numbers on a monitor. I've got 59k and 99% of the time I just go for an extended ride until regen is complete. Only regen related component failure was the def tank heater, which was warrantied.
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Old 01-21-2019, 10:28 AM   #26 (permalink)
Dmax Dually
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I don't even know if my DEF tank heater works or was ever turned on since it was built....I live in FL so their is no need for it....Does the ECM ever check /test the heater???
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Old 01-21-2019, 12:34 PM   #27 (permalink)
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Quote:
Originally Posted by jerkyboy View Post
I agree with a lot of what's been said about reading too much into the regen numbers on a monitor. I've got 59k and 99% of the time I just go for an extended ride until regen is complete. Only regen related component failure was the def tank heater, which was warrantied.
Just FYI, DEF has nothing to do with regeneration.
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Old 01-21-2019, 01:46 PM   #28 (permalink)
Ted White
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The one indirect connection between DEF and regeneration is at the END of the regen cycle. DEF is injected to help cool the DPF/SCR after regen completes.
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Old 01-21-2019, 01:54 PM   #29 (permalink)
redwngr
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Quote:
Originally Posted by Dmax Dually View Post
I don't even know if my DEF tank heater works or was ever turned on since it was built....I live in FL so their is no need for it....Does the ECM ever check /test the heater???
Probably.

And probably more than one type of check.


There are 100's and 100's of fault codes on these trucks.
Many can be caused by more than one thing.
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