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Hi, new forum member & new Colorado diesel owner. I took ownership of a Z-71 4 door short box in November (2019 model year). It has been a great truck with the exception of some emission related issues. I will explain the situation and see if anyone else has experienced the same issues and can offer some advice because my dealer does not give me a warm fuzzy feeling on solving the issue (numerous emails & calls and two shops visits so far)....

In mid February, at about 3,500 miles on the odometer, I had a CEL and the following two codes as verified with my code reader and dealer: P244A (DPF differential pressure too low bank 1, and P226D DPF deteriorated/missing substrate bank 1. The first trip to the local dealer cleared the faults and they said if the faults show up again, we will order & install a new DPF. Well the faults came back in a short time and they did indeed install a new DPF. The new filter worked fault free for about a week and the same two faults have re-occurred. On top of the faults, I also got the “engine power is reduced” message and it was indeed reduced. These faults have been clearing on their own or I have been clearing them with my code reader. I will also throw in I live in northern Minnesota and saw plenty of action in the -20 to -30 below zero temps during this time. The truck has been starting great both plugged in and not, so no issues there. Also curious is the DEF usage is all over the map according to my DEF % gauge. It may go way longer than the GM estimated usage amount or go way shorter before the gauge changes. Before the dealer changed out the DPF, it stayed at ~90% for a month or so (it was very cold during that time). So for anyone with experiences with these faults, maybe they can chime in and advise on the situation. I get the feeling this will be a lengthy troubleshooting exercise for the dealer, and I would rather drive my truck than some loaner vehicle. Here are a few questions I have and have not been able to find concrete data on:

Is the lack of DEF usage (according to my % use gauge) anything to be concerned about? It freezes at 12°f and is maybe a block of ice all winter (where I live). The DEF level does vary +/- a few % at times, not sure how it can measure frozen material or how good the heaters work for melting the DEF ( I guess it is slowly trending downward over time indicating some usage).

Concerning the two faults, I have seen no indication if regens are occurring as I drive. Hard to believe one DPF was plugged (as the dealer thought), and then have the same faults occur with the new DPF (looking as if this one is plugged also).

I don’t quite understand if there is an interaction with the DEF and the DPF, as diesel fuel is injected into the SCR converter to create the high temps needed for the DPF rejen cycle and NOX reduction. So life goes on without DEF use? Isn’t that what other manufactures got in a jackpot over?


It is shitty weather to be crawling underneath the vehicle, but I do plan to check on the emission related components (wires, leaks, and connections, etc) while working with the dealer in hopes this does not turn in to a lemon law situation because I really like what the truck offers. The delete routine might solve all of this, but I hate to void the warranty and piss off mother nature. Thanks for any advice on the matter…
 

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DEF usage: The DEF usage is based on how hard you work the truck I believe or how much you drive I think one time I went 3000 miles and had to fill it back up (added just 2.5 gallons so not completely full) And another time I think I went over 5000 miles on just 2 1/2 gallons. As to why yours is not going down very slowly, not really sure but if you’re not working the truck or driving a lot then perhaps this reasoning is why.

DPF and Regen: You don’t ever really know that your truck is going through a regen, so long as you get up to highway speeds (or at least 45 mph or more) to get the DPF Hot enough to where it can complete a burn. The only way that you will know that it is doing a regeneration is if you watch your instant miles per gallon and you’ll see them drop off considerably compared to what they normally are. Also you may notice that during a regeneration your truck seems more peppy and has more power. I think that has Something to do with the added fuel being used to complete the burn or perhaps the EGR is closed off. Can’t quite remember.

The only time you’ll see a regen message appear is if you do a bunch of city driving and short drives where you don’t get the truck up to operating temp. Then you’ll finally see a message that says DPF cleaning please keep driving or some bull crap like that. Otherwise it will occur in the background and you will never really know it is happening.

The DPF and DEF usage have no correlation with each other.

One final note in regards to your wanting to delete the truck. If you have a 2019 model year truck, You can tune the truck but no tuner out there yet has the ability to do the delete portion of the truck for tune. GM is making it harder and harder to bypass the computer system. And make it think that everything is still connected. I don’t know if any tuners are working on it or not. So for now, 2019 and newer trucks cannot be deleted.
 

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DEF usage: The DEF usage is based on how hard you work the truck I believe or how much you drive I think one time I went 3000 miles and had to fill it back up (added just 2.5 gallons so not completely full) And another time I think I went over 5000 miles on just 2 1/2 gallons. As to why yours is not going down very slowly, not really sure but if you’re not working the truck or driving a lot then perhaps this reasoning is why.

DPF and Regen: You don’t ever really know that your truck is going through a regen, so long as you get up to highway speeds (or at least 45 mph or more) to get the DPF Hot enough to where it can complete a burn. The only way that you will know that it is doing a regeneration is if you watch your instant miles per gallon and you’ll see them drop off considerably compared to what they normally are. Also you may notice that during a regeneration your truck seems more peppy and has more power. I think that has Something to do with the added fuel being used to complete the burn or perhaps the EGR is closed off. Can’t quite remember.

The only time you’ll see a regen message appear is if you do a bunch of city driving and short drives where you don’t get the truck up to operating temp. Then you’ll finally see a message that says DPF cleaning please keep driving or some bull crap like that. Otherwise it will occur in the background and you will never really know it is happening.

The DPF and DEF usage have no correlation with each other.

One final note in regards to your wanting to delete the truck. If you have a 2019 model year truck, You can tune the truck but no tuner out there yet has the ability to do the delete portion of the truck for tune. GM is making it harder and harder to bypass the computer system. And make it think that everything is still connected. I don’t know if any tuners are working on it or not. So for now, 2019 and newer trucks cannot be deleted.
Thanks for the reply Burgess159. The info you provided helps to get a better picture of how the emission system should be working. As far as my truck goes with the last week of weather above freezing temps, all has been well with the DEF % dropping as the miles increase and have not had any faulting related to the DPF system. Will continue to monitor and report any updates. Thanks again...
 

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Hi, new forum member & new Colorado diesel owner. I took ownership of a Z-71 4 door short box in November (2019 model year). It has been a great truck with the exception of some emission related issues. I will explain the situation and see if anyone else has experienced the same issues and can offer some advice because my dealer does not give me a warm fuzzy feeling on solving the issue (numerous emails & calls and two shops visits so far)....

In mid February, at about 3,500 miles on the odometer, I had a CEL and the following two codes as verified with my code reader and dealer: P244A (DPF differential pressure too low bank 1, and P226D DPF deteriorated/missing substrate bank 1. The first trip to the local dealer cleared the faults and they said if the faults show up again, we will order & install a new DPF. Well the faults came back in a short time and they did indeed install a new DPF. The new filter worked fault free for about a week and the same two faults have re-occurred. On top of the faults, I also got the “engine power is reduced” message and it was indeed reduced. These faults have been clearing on their own or I have been clearing them with my code reader. I will also throw in I live in northern Minnesota and saw plenty of action in the -20 to -30 below zero temps during this time. The truck has been starting great both plugged in and not, so no issues there. Also curious is the DEF usage is all over the map according to my DEF % gauge. It may go way longer than the GM estimated usage amount or go way shorter before the gauge changes. Before the dealer changed out the DPF, it stayed at ~90% for a month or so (it was very cold during that time). So for anyone with experiences with these faults, maybe they can chime in and advise on the situation. I get the feeling this will be a lengthy troubleshooting exercise for the dealer, and I would rather drive my truck than some loaner vehicle. Here are a few questions I have and have not been able to find concrete data on:

Is the lack of DEF usage (according to my % use gauge) anything to be concerned about? It freezes at 12°f and is maybe a block of ice all winter (where I live). The DEF level does vary +/- a few % at times, not sure how it can measure frozen material or how good the heaters work for melting the DEF ( I guess it is slowly trending downward over time indicating some usage).

Concerning the two faults, I have seen no indication if regens are occurring as I drive. Hard to believe one DPF was plugged (as the dealer thought), and then have the same faults occur with the new DPF (looking as if this one is plugged also).

I don’t quite understand if there is an interaction with the DEF and the DPF, as diesel fuel is injected into the SCR converter to create the high temps needed for the DPF rejen cycle and NOX reduction. So life goes on without DEF use? Isn’t that what other manufactures got in a jackpot over?


It is shitty weather to be crawling underneath the vehicle, but I do plan to check on the emission related components (wires, leaks, and connections, etc) while working with the dealer in hopes this does not turn in to a lemon law situation because I really like what the truck offers. The delete routine might solve all of this, but I hate to void the warranty and piss off mother nature. Thanks for any advice on the matter…

Ive been battling with my emissions system (DEF Pump and control module) for about 2 years. Been to the dealer multiple times (5-6 times on the issue). Had the pump, tank and/or control module replaced multiple times. Now at 33k miles and about to give up. I haven't seen many problems like mine, so I think I just got a lemon.
 

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Yes, have had those codes repeatedly on my 2017 along with other check engine codes. About every 3,500 miles. Currently pursuing GM on lemon law, 5 check engines in 1.5 years and 18,000 miles. It is clear dealer has no clue they replaced entire def system and code came back. Last two times they simply reflashed EM and sent me on my way. Oddly enough, GM requisitioned vehicle for extended emissions testing by a firm in Ann Arbor. They kept truck for 2 weeks paid me $300 and provided a rental. Never got a report on tests.
Ive been battling with my emissions system (DEF Pump and control module) for about 2 years. Been to the dealer multiple times (5-6 times on the issue). Had the pump, tank and/or control module replaced multiple times. Now at 33k miles and about to give up. I haven't seen many problems like mine, so I think I just got a lemon.
 

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Ive been battling with my emissions system (DEF Pump and control module) for about 2 years. Been to the dealer multiple times (5-6 times on the issue). Had the pump, tank and/or control module replaced multiple times. Now at 33k miles and about to give up. I haven't seen many problems like mine, so I think I just got a lemon.
delete.jpg


Seriously though. If you like the truck otherwise, and live in a state or area of your state that doesn't do emissions testing, than delete it and be done with your DPF and DEF problems.
 

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Yes, have had those codes repeatedly on my 2017 along with other check engine codes. About every 3,500 miles. Currently pursuing GM on lemon law, 5 check engines in 1.5 years and 18,000 miles. It is clear dealer has no clue they replaced entire def system and code came back. Last two times they simply reflashed EM and sent me on my way. Oddly enough, GM requisitioned vehicle for extended emissions testing by a firm in Ann Arbor. They kept truck for 2 weeks paid me $300 and provided a rental. Never got a report on tests.
 

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I have a 2018 Colorado diesel nothing but head aches Started with limp mode when towing. Kept changing sensor. Then poor def. limp mode back. New turbo Oct 2019. No more limp mode yet but now emissions code and reduced speed Back to dealer
Tomorrow. Not happy had two Silverados with no issues since 2006. Fed up with this lemon. 30000 kilometres and in shop once a month on average Piece of junk
 

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I have a 2018 Colorado diesel nothing but head aches Started with limp mode when towing. Kept changing sensor. Then poor def. limp mode back. New turbo Oct 2019. No more limp mode yet but now emissions code and reduced speed Back to dealer
Tomorrow. Not happy had two Silverados with no issues since 2006. Fed up with this lemon. 30000 kilometres and in shop once a month on average Piece of junk
Sorry to hear that, I have a 2018 and had no issues whatsoever until 57K and it was the secondary fuel injector which was covered under the extended warranty I guess maybe I got lucky or you have bad luck one or the other
 

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My 2016 is over 60,000 now. No issues, but if I had some of the problems others seem to have, My happy little ass would be deleting as fast as I could. Then a trip to Canada. Oh' Canada!
 

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Just DEF system issues here. I'm over 60k now and had Poor DEF quality issues and a fault code for the DEF pump. Can't remember off the top of my head what the code was, but the dealer replaced some parts.

Service tech said he's seen a lot of Colorados and Canyons come in for DEF and DPF issues. He said both very hot and very cold weather cause issues due to some poor design decisions.

Very cold weather (multiple days below 20F, nights below 0F) tends to cause slushing or freezing due to crummy design, so you'll get the poor quality DIC message and a countdown from 100 miles to partial limp (65 mph). If you garage the truck, it can cause the message to go away after driving for a short distance.

I found a PIP and bulletin from GM on the NHTSA site on Frozen Tank status:
Very warm temps (above 77F) can also cause problems in the DEF system, so it's a lovely catch-22 system.

I'm gathering parts from sources to "fix" mine permanently once it's past the 80k warranty - probably next year. That's the only long-term solution I can figure out at this point.
 
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