Chevy and GMC Duramax Diesel Forum banner
  • Hey Everyone! Enter your ride HERE to be a part of this months Ride of the Month Challenge!
1 - 20 of 32 Posts

· Registered
Joined
·
212 Posts
Discussion Starter · #1 ·
I recall seeing discussions about how often our trucks need regeneration as well as the impact of city driving on this. I have not noticed any discussions about how many miles it takes to complete regeneration once it starts. I have an iDash so that makes it easy to anticipate regeneration cycles and to monitor those once they begin.

I have a 2021 GMC 3500HD and curious what others are experiencing for the duration of the regeneration once it starts. For comparison purposes my truck routinely requires about 40 miles of highway driving to successfully complete a regeneration. That is about double what my 2018 GMC 2500HD required. I am curious about why my 2021 Duramax requires so many more miles to complete the regen cycle. On a positive note, I do also average about 800 miles between my regeneration cycles. I did ask a local GMC service writer if there were any ECU updates related to the duration of regeneration cycles and he reported none after looking at his computer for awhile.
 

· Registered
Joined
·
555 Posts
I have an iDash in my 21 and average just over 800 miles between regens and takes about 40 miles to complete. On my 15 it averaged around 725 miles between regens and would take about 35 miles to complete.

Another difference I notice is when it is regen, the RPMs aren’t high like they would be on my 15.

I have heard the 17-19 L5P would regen more frequently and I was expecting that with my 21, but I am not seeing.
 

· Registered
2021 Silverado 2500HD LTZ L5P
Joined
·
781 Posts
I recall seeing discussions about how often our trucks need regeneration as well as the impact of city driving on this. I have not noticed any discussions about how many miles it takes to complete regeneration once it starts. I have an iDash so that makes it easy to anticipate regeneration cycles and to monitor those once they begin.

I have a 2021 GMC 3500HD and curious what others are experiencing for the duration of the regeneration once it starts. For comparison purposes my truck routinely requires about 40 miles of highway driving to successfully complete a regeneration. That is about double what my 2018 GMC 2500HD required. I am curious about why my 2021 Duramax requires so many more miles to complete the regen cycle. On a positive note, I do also average about 800 miles between my regeneration cycles. I did ask a local GMC service writer if there were any ECU updates related to the duration of regeneration cycles and he reported none after looking at his computer for awhile.
I go about 650 to 700 between regens sometimes I go the fuel limit. When I'm doing a lot of highway its 800. Just depends on how i have been using the truck. I keep an eye on it with the idash. I have noticed in the cold I'm using a lot more def than in summer
 

· Registered
Joined
·
212 Posts
Discussion Starter · #4 ·
I go about 650 to 700 between regens sometimes I go the fuel limit. When I'm doing a lot of highway its 800. Just depends on how i have been using the truck. I keep an eye on it with the idash. I have noticed in the cold I'm using a lot more def than in summer
JonM21Ltz: how many miles does it take to complete your regions?
 

· Registered
2021 Silverado 2500HD LTZ L5P
Joined
·
781 Posts
JonM21Ltz: how many miles does it take to complete your regions?
Depends on how fast I'm going. I've tried it on interstate back roads and around town from 30 to 75mph. When I drive at higher speed it's done in around 20 to 25 miles. 45 to 55 takes around 30 miles 30 to 45 almost 40 miles. The higher you can maintain speed the quicker it goes.

I haven't made hard notes on it. But I've gotten good results at any speed in terms of getting the soot percent to zero. The only time I've had issue with regen was the time I intentionally interrupted the regen let the truck sit until it cooled off then resumed. It finished the regen but the following regen came really early at the 400 mile mark. I'm not willing to do that again if I can help it.

Last two regens I've done a lot of idling and short trips. As long as I do an uninterrupted regen it doesnt seem to care. The only time I've had poor results on regen was the interrupted one I did. I'm pretty convinced at this point that interrupting regens is a bad idea.

If your doing a regen plan on 45 minutes

These are my impressions nothing scientific at all and I could be wrong in my assumptions
 

· Registered
Joined
·
555 Posts
Depends on how fast I'm going. I've tried it on interstate back roads and around town from 30 to 75mph. When I drive at higher speed it's done in around 20 to 25 miles. 45 to 55 takes around 30 miles 30 to 45 almost 40 miles. The higher you can maintain speed the quicker it goes.

I haven't made hard notes on it. But I've gotten good results at any speed in terms of getting the soot percent to zero. The only time I've had issue with regen was the time I intentionally interrupted the regen let the truck sit until it cooled off then resumed. It finished the regen but the following regen came really early at the 400 mile mark. I'm not willing to do that again if I can help it.

Last two regens I've done a lot of idling and short trips. As long as I do an uninterrupted regen it doesnt seem to care. The only time I've had poor results on regen was the interrupted one I did. I'm pretty convinced at this point that interrupting regens is a bad idea.

If your doing a regen plan on 45 minutes

These are my impressions nothing scientific at all and I could be wrong in my assumptions
I have had a couple interrupted regens and never experienced what you have when a regen was interrupted. Even with the 15 I had when a regen was interrupted, next regen was normal for mileage and soot level
 

· Registered
2021 Silverado 2500HD LTZ L5P
Joined
·
781 Posts
I have had a couple interrupted regens and never experienced what you have when a regen was interrupted. Even with the 15 I had when a regen was interrupted, next regen was normal for mileage and soot level
I dont knowing it was one off I've only had it happen once when when I had less than 3000 miles on it and had the idash going. It was right after I started using the idash to keep an eye on it and I haven't had to interrupt a regen since. It's the only time I've gotten less than 600 miles between regens since I started monitoring regens.

The only other weirdness is the soot % jumps up a lot then backs down a lot all through the drive cycle between regens and plateaus a lot it doesnt seem to be using any more fuel than normal during those swings. Some people have called it passive regen but the temps do not go up or deviate from the norm.
 

· Registered
Joined
·
212 Posts
Discussion Starter · #8 ·
Depends on how fast I'm going. I've tried it on interstate back roads and around town from 30 to 75mph. When I drive at higher speed it's done in around 20 to 25 miles. 45 to 55 takes around 30 miles 30 to 45 almost 40 miles. The higher you can maintain speed the quicker it goes.

I haven't made hard notes on it. But I've gotten good results at any speed in terms of getting the soot percent to zero. The only time I've had issue with regen was the time I intentionally interrupted the regen let the truck sit until it cooled off then resumed. It finished the regen but the following regen came really early at the 400 mile mark. I'm not willing to do that again if I can help it.

Last two regens I've done a lot of idling and short trips. As long as I do an uninterrupted regen it doesnt seem to care. The only time I've had poor results on regen was the interrupted one I did. I'm pretty convinced at this point that interrupting regens is a bad idea.

If your doing a regen plan on 45 minutes

These are my impressions nothing scientific at all and I could be wrong in my assumptions
Thanks for sharing your experience. I have tried different highway speeds to improve my required miles to complete regeneration but mostly between 60 and 70 and not noticed much difference besides making my reported mpg drop even worse. I seem to routinely stay close to the 40 mile mark including when I am pulling a trailer. I have thought about trying either to drive well over 70 or maybe using manual shifting to hold the truck in 9th gear to increase my RPM.

I have had just one interrupted regeneration which involved driving around town and making stops in-between some highway miles. It took for ever to complete almost like it had to start over again once I was at highway speeds. Once completed the driven miles to my next regeneration was typical for me. I use the iDash to avoid these interrupted regens by triggering a mobile regen when I am confident I can allow it to complete.
 

· Registered
Joined
·
212 Posts
Discussion Starter · #9 ·
The only other weirdness is the soot % jumps up a lot then backs down a lot all through the drive cycle between regens and plateaus a lot it doesnt seem to be using any more fuel than normal during those swings. Some people have called it passive regen but the temps do not go up or deviate from the norm.
My soot % will also jump around a bit then back down as well. If I see my soot % increasing faster than I would like, I have tried some hard accelerations once the truck is fully warmed up and that seems to have a positive effect on helping to push the soot % back down.
 

· Administrator
Joined
·
3,151 Posts
Something that appears to help speed up the process on my '19 is to go to manual shift mode and lock out 6th gear. My daily commute is highway, so when I do this I try to maintain 65 mph in 5th gear which is around 1800 RPM.
It might be something for you guys to try.

I also don't bother watching SL unless I'm in a regen event. It does count down during the regen giving you an idea of how much longer it will take. When I'm not in regen, I watch the RGN trigger which consistently increases until the truck wants to start a regen.
 
  • Like
Reactions: nutdriver

· Registered
2022 1500 CCSB Sierra AT4 3.0L I6 Duramax
Joined
·
303 Posts
around town short trips under 20 miles I can see regens happen at 600 miles. Out on the highway for a long trip I have gone almost 900 miles before it kicks in.

once it starts it takes from 25 miles on the highway at speed, to almost double that if I am only doing stop and go traffic.

it absolutely destroys my fuel mileage...
 

· Registered
Joined
·
3 Posts
I recall seeing discussions about how often our trucks need regeneration as well as the impact of city driving on this. I have not noticed any discussions about how many miles it takes to complete regeneration once it starts. I have an iDash so that makes it easy to anticipate regeneration cycles and to monitor those once they begin.

I have a 2021 GMC 3500HD and curious what others are experiencing for the duration of the regeneration once it starts. For comparison purposes my truck routinely requires about 40 miles of highway driving to successfully complete a regeneration. That is about double what my 2018 GMC 2500HD required. I am curious about why my 2021 Duramax requires so many more miles to complete the regen cycle. On a positive note, I do also average about 800 miles between my regeneration cycles. I did ask a local GMC service writer if there were any ECU updates related to the duration of regeneration cycles and he reported none after looking at his computer for awhile.
Hello dump question. I have a SRW 2021 GMC 3500 Diesel. How or when does it tell you, Its in Regen. I gave yet to know when it does any of it. As of now I have 41K Miles.
 

· Registered
Joined
·
1,727 Posts
It doesn't. No light, no message. If it's in a regen and you come to a stop, or put the truck in park the idle will be higher and it will feel a little quicker off the line because its in regen. There will also be a noticeable small when it is regening as well (and your windows are down and/or you are at a stop) If you are outside of the truck while it is running at idle you'll feel some heat from the exhaust area and back end too.
 

· Registered
Joined
·
47 Posts
Hello dump question. I have a SRW 2021 GMC 3500 Diesel. How or when does it tell you, Its in Regen. I gave yet to know when it does any of it. As of now I have 41K Miles.
People that are talking with a high degree of specificity probably have an iDash or equivalent.

GoBlowSnow mentioned some indicators, but I think the clearest one is when your instantaneous fuel econmy drops dramatically for no other apparent reason.
 

· Registered
2021 Silverado 2500HD LTZ L5P
Joined
·
781 Posts
It doesn't. No light, no message. If it's in a regen and you come to a stop, or put the truck in park the idle will be higher and it will feel a little quicker off the line because its in regen. There will also be a noticeable small when it is regening as well (and your windows are down and/or you are at a stop) If you are outside of the truck while it is running at idle you'll feel some heat from the exhaust area and back end too.
You need an idash or some other after market monitor to see exactly what is happening. The truck all by itself wont tell you. Personally I think not having that info is on par with riding around without a fuel gauge....

I use an idash because it's small and you get a lot of info in that tiny footprint
 

· Registered
Joined
·
7,677 Posts
I don't think it's necessary to know when it is in regen.
I've had LMM, LML, L5P and now LM2 dmaxes.
Didn't have LMM long, and traded it for an LML when the '11's were released with all the improved chassis and powertrain features.

Anyway, don't recall how long LMM took for regen.
LML -- about 30 minutes
L5P -- about 20 minutes
LM2 -- about 12 minutes

Miles/time longer if the trip involves a bunch of stopped/idling/stop and go/etc.

Likely won't know it occurred if running down the freeway and not monitoring fuel economy.

All have slightly higher idle if brought to a stop during regen.
All have slightly different exhaust tone during regen. Might not be noticeable except at very slow speeds or when at idle.
All will show fuel economy significantly less expected for current operating conditions if in regen.

Also ran an LLY for a bunch of years before the LMM.
This is the first truck I've added a monitor.

Great entertainment!

I've created a log of every regen this 3.0 has done.
I don't do anything different when they occur.

If truck is parked and shut off during regen -- it will generally resume the next trip.
If it was close to being finished, it may not resume, but instead will wait until the next regen trigger.


GM intended that regen have no impact on driving -- so there is no indicator.
The keep driving message mentioned in the diesel supplement only occurs if the truck is unable use regens to reduce the soot levels. Most will likely never see this message.
 

· Registered
Joined
·
7,677 Posts
More regen information:


The Diesel Exhaust System and DPF Soot Accumulation
August 24, 2020
The diesel exhaust system on 2017-2018 Silverado and Sierra models and 2019-2020 Silverado 2500/3500 and Sierra 2500/3500 models equipped with the 6.6L Duramax diesel engine (RPO L5P) (Fig. 1) requires an occasional Diesel Particulate Filter (DPF) cleaning. Under normal driving conditions, the DPF cleaning occurs without any driving involvement. However, there may be circumstances that require a service regeneration to be performed.
Fig. 1
DPF Soot Level

Beginning with 2017 Silverado and Sierra models, the DPF Soot Accumulation is measured in percent instead of grams in GDS 2. The ECM will not try to perform a regeneration until the DPF Soot Accumulation increases to approximately 100%. If the DPF Soot Accumulation increases to 115% and the system has not been able to regenerate, the “Continue Driving” message will display on the Driver Information Center (DIC). If the DPF Soot Accumulation increases to 140%, DTC P2463 (DPF Soot Accumulation) will set and a service regeneration will be required to clean the DPF.
There are two soot level readings in GDS2. One uses the differential pressure sensor to calculate the soot in the DPF and the other uses other engine data. If either of these reaches the threshold, a regeneration will be performed.

Service Regeneration
A Service Regeneration is designed to lower the soot accumulation in the DPF in a very controlled way. It is not as effective at lowering the soot accumulated in the DPF as a Regeneration Enable followed by a drive.
Only perform a service regeneration if instructed in the appropriate Service Information. If there is a concern about the DPF Soot Accumulation, perform a regeneration enable and return the vehicle to the customer.

Vehicle Idling
Some vehicles may spend a lot of time idling. Use the following steps to aid in determining the equivalent mileage (kilometers):
  1. Record the total engine hours indicated on the DIC.
  2. Multiply the engine hours by 33 miles or 53 km. This represents an average speed of 33 MPH or 53 KM/H.
  3. The result should be close to or lower than the mileage on the odometer.
For example, if a vehicle has 1812.3 engine hours and 60,837 miles (97,908 km) on the odometer, the engine run time would equate to about 59,806 miles (96,052 km) (1812.3 X 33 = 59,806) (1812.3 X 53 = 96,052).
Since the calculated mileage is less than the actual mileage, the vehicle does not spend an excessive amount of time idling.
If the calculated mileage is more than the actual mileage, the vehicle would be considered a vehicle that idles a lot and this information may be useful in diagnosing any issues.
TIP: The engine hours formula should be used to aid in engine diagnosis only. It should not be used to determine any warranty claims.

How Regeneration Should Occur
The DPF traps the soot generated as a part of the normal operation of a diesel engine so that it is not sent into the environment. The process of regeneration enables the vehicle to clean the filter so it can trap more soot. Factors that determine when the ECM will try to perform a regeneration include:
    • After approximately 36 gallons (136 L) of fuel used since the last regeneration.
    • A maximum distance of 800 miles (1287 km) have been traveled since the last regeneration.
    • A pre-determined number of engine hours since the last regeneration.
    • A calculated or measured soot mass of 100% in the particulate filter.
When any of the above criteria are met, the ECM will perform a regeneration as soon as all the correct conditions are met. If the ECM cannot perform a regeneration, the ECM will only look at the soot mass to determine to display the Continue Driving DIC message or to set DTC P2463.

The ECM uses the following criteria to perform a regeneration:
    • Vehicle in Drive
    • BARO sensor 1 is more than 51 kPa (7.4 PSI)
    • Engine speed between 500 and 4000 RPM
    • Exhaust Gas Temperature Sensor 1 between 100 and 725 C
    • Exhaust Gas Temperature Sensor 2 between 95 and 750 C
    • Exhaust Gas Temperature Sensor 3 between 0 and 750 C
    • Exhaust Gas Temperature Sensor 4 between 60 and 750 C
    • Exhaust Gas Temperature Sensor 4 between 60 and 850 C
    • Engine Coolant Temperature between 50 and 140 C
    • Intake air temperature between -70 and 250 C
    • Fueling from -1 to 165mm3
    • Vehicle speed from -1 to 160 km/hr
    • No active DTC related to EGR, Indirect injector, or Throttle (boost)
The vehicle does not have a soot level sensor to determine how much soot is in the DPF. It uses algorithms to calculate the soot mass.

DTC P2463
When DTC P2463 sets, the ECM will no longer try to perform a driving regeneration and the vehicle will require the more controlled service regeneration. There are a number of factors that can cause the code to set, including:
    • The driver ignoring the Continue Driving messages
    • Leaks from intake or exhaust system
    • Poor fueling in the engine
    • Contaminated or bad fuel
    • Externally damaged or worn components.
    • Loose or improperly installed components
    • Dirty components (air filter or TMAP sensor)
    • Driving style, such as binary driving (frequently on/off accelerator or brake)

High Soot Levels
Factors that contribute to generating high levels of soot include:
    • Charge air cooler (CAC) and Air induction system leaks.
    • A restricted air filter.
    • Exhaust system leaks that may cause inaccurate Exhaust Gas Temperature sensor or Exhaust Pressure Differential sensor values.
    • Failed, intermittent, improperly installed, incorrectly wired or loose Exhaust Gas Temperature sensors may cause inaccuracies in the soot model. Look at all temperature sensors when the vehicle is cold to verify that they read close to each other.
    • Improperly routed differential pressure lines. The exhaust differential pressure line should have a continuous downward gradient without any sharp bends or kinks from the sensor to the DPF.
    • Leaks or internal restrictions from the Exhaust Pressure Differential sensor lines.
    • A skewed or shifted Exhaust Pressure Differential sensor will cause inaccuracies in the soot model.
    • A cracked or damaged MAF sensor housing.
    • A skewed, stuck in range, or slow responding MAF sensor. Inspect the MAF sensor for contamination.
    • Indirect Fuel Injector leaking or restricted.
    • Externally damaged or worn components.
    • Loose or improperly installed components.
    • Water in fuel contamination.
    • Engine mechanical condition, such as low compression.
    • Vehicle Modifications

Reducing the Number of DPF Regenerations
If a customer asks what can be done to reduce the number of DPF regenerations needed. Explain that when the “Continue Driving“ message is displayed (Fig. 2), the vehicle should be driven safely at a steady speed as close to the posted speed limit as possible, until the message turns off, which can take up to 30 minutes.
Fig. 2
In addition, driving with cruise control when possible will help the engine perform more efficiently as well as help the engine burn cleaner, resulting in less regenerations.
Driving at a steady pace without aggressive throttle application also will reduce the amount of soot generated by the system.
When descending an incline, use Tow/Haul mode to help with the ability of the vehicle to perform a regeneration.
The use of the diesel exhaust brake on declines will also help adjust the gearing to allow the vehicle to perform a regeneration. Keep in mind that on 2020 models, the diesel exhaust brake may not be as noticeable as in prior model year vehicles.
 

· Registered
Joined
·
7,677 Posts
Regen interval.
This is latest chart update for my LM2 (none of the others had regen interval data recorded)


Interval is depends on how it is used.
In this chart, all the 'long' intervals occurred when the interval included some (or all) towing.

Day to day driving MY USAGE seems to run about 250 miles.

All in, including the towing, average interval is 300 miles.

Azure Plot Rectangle Slope Parallel
 

· Registered
‘22 Sierra SLT 3500 DRW; Edge CTS3 Insight: MBRP 4”
Joined
·
61 Posts
Just finished a run from SD to ME and back. Regens we’re like clockwork at 808 miles. Some times the “soot” level on the Edge was at/near 100%. Twice it was at 57 and 65% respectively. Was keeping track of miles on Trip 2. At 805-806 miles travelled, the warming would start and come full in at 808.
If the spot level was lower than 100%, it would immediately jump to 100 then work it’s way down from there. All regens were complete within 37-42 miles driven.
Other key indicators were mpg dropping off significantly (6-7 pts). Keep an eye on your DEF levels. I try not to let it get below half. Big rig driving was basically the same for DEF levels…below half and freezing temps made for a very unhappy DEF warming system and caused all sorts of annoyances.
 
1 - 20 of 32 Posts
Top