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Discussion Starter · #1 ·
I have seen some talk on the forum about DPF cleaning but haven't seen anything from anyone who actually had it done. My dealer recommended replacing most of the exhaust system after diagnosing a CEL as clogged DPF. The dealer said there was nothing wrong with the regens - I haven't hooked up the OBD yet to verify. The truck still ran fine but the mileage seemed to drop off a bit. I chose to clean the DPF instead. I found several local places that would clean the DPF (I live in Salt Lake City) but they all required the DPF to be taken off by someone else and delivered to them. I had a muffler shop remove the DPF and catalytic converter (the shop that did the cleaning strongly urged me to do both) and carried them to the cleaning shop. They cut both open, cooked them both overnight at around 1200 deg, and then did a solvent cleaning. They didn't have a way to measure the change in flow resistance (didn't fit in their testing equipment) but said that subjectively they both seemed to flow much better. The muffler shop reinstalled everything and reset the sensors and now there is no CEL. I haven't driven it enough to see if the mileage changed. So far it seems like this has worked well. It was a minor hassle running parts around but I saved about $1000 (total cost was $240 for the remove/replace and $811 for cleaning both). Both shops said they should be able to do this several times before the R&R and cutting the exhaust off and the cans open became too hard.

The muffler shop said they normally only see DPFs needing cleaning on trucks so clogged that they barely run and suggested if this happens again to do a forced regen or 2 to see if that works.

Curious to hear any criticism or thoughts on this. And hoping this info can help others.
 

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I have seen some talk on the forum about DPF cleaning but haven't seen anything from anyone who actually had it done. My dealer recommended replacing most of the exhaust system after diagnosing a CEL as clogged DPF. The dealer said there was nothing wrong with the regens - I haven't hooked up the OBD yet to verify. The truck still ran fine but the mileage seemed to drop off a bit. I chose to clean the DPF instead. I found several local places that would clean the DPF (I live in Salt Lake City) but they all required the DPF to be taken off by someone else and delivered to them. I had a muffler shop remove the DPF and catalytic converter (the shop that did the cleaning strongly urged me to do both) and carried them to the cleaning shop. They cut both open, cooked them both overnight at around 1200 deg, and then did a solvent cleaning. They didn't have a way to measure the change in flow resistance (didn't fit in their testing equipment) but said that subjectively they both seemed to flow much better. The muffler shop reinstalled everything and reset the sensors and now there is no CEL. I haven't driven it enough to see if the mileage changed. So far it seems like this has worked well. It was a minor hassle running parts around but I saved about $1000 (total cost was $240 for the remove/replace and $811 for cleaning both). Both shops said they should be able to do this several times before the R&R and cutting the exhaust off and the cans open became too hard.

The muffler shop said they normally only see DPFs needing cleaning on trucks so clogged that they barely run and suggested if this happens again to do a forced regen or 2 to see if that works.

Curious to hear any criticism or thoughts on this. And hoping this info can help others.
I think they should have used a bore scope and showed you the DPF media before and after. Better yet would have been for you to be able to view it pre and post to quantify the results.

Could you please add your truck particulars to your "signature" so when you ask questions we have a starting point. Also out of curiosity could you define "but the mileage seemed to drop off a bit" so we can compare to our vehicles. Your mileage would be of help as well and your typical driving routines, mostly short trips, mostly long trips and so on. Also where in the country do you live? is it cold most of the time. Any info and the more info that you provide will start the minds on the board churning.
 

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Discussion Starter · #3 ·
Good points. My truck is a 2019 with 76k miles. No tune or deletion. It has lived mostly in Utah and Idaho so it's seen temps ranging from -22 to 107 deg F. Most of my driving has been on the highway (~45mph ave speed since new), I've towed several thousand miles, mostly with a 1800 lb trailer and maybe 500 easy miles with a 5k lb trailer and I never, ever idle it for more than about a minute. About the time the CEL came on, my mileage on a trip that I do often dropped from about 26 mpg to 21, but I was also in a fair bit of snow and cold temps. I didn't drive it long enough in that state to be confident that mileage had dropped due to the DPF.

My point wasn't to ask why I got the CEL and for suggestions to keep this from happening again - that is obviously interesting to me but has been discussed a lot. When I searched the forum for help, it appeared that there has been a lot of discussion about this topic including the option of cleaning the DPF vs replacing the whole system, but I couldn't find any account of someone actually having the cleaning done. It took me a while to figure out where to go and confirm that this process included both a muffler shop and a DPF cleaning shop. That now makes more sense as their business is nearly all big rigs with DPFs designed for easy removal. The shop I went to had never done a Colorado but was confident that they could figure it out. It felt like a gamble to me, but I was willing to take that chance. The dealer diagnosed the problem and immediately recommended I replace most of the exhaust system for around $2k which sounded typical from reading this forum. I told them I was going to go the cleaning route and they were curious about that but thought it sounded like a good idea and were supportive.

In retrospect I wish I had done a little more verification like you suggest and verifying that my regens had been happening regularly. Priorities change a bit when you are in a blizzard cycle, have an upcoming trip, and are swamped with unexpected work.
 

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Good points. My truck is a 2019 with 76k miles. No tune or deletion. It has lived mostly in Utah and Idaho so it's seen temps ranging from -22 to 107 deg F. Most of my driving has been on the highway (~45mph ave speed since new), I've towed several thousand miles, mostly with a 1800 lb trailer and maybe 500 easy miles with a 5k lb trailer and I never, ever idle it for more than about a minute. About the time the CEL came on, my mileage on a trip that I do often dropped from about 26 mpg to 21, but I was also in a fair bit of snow and cold temps. I didn't drive it long enough in that state to be confident that mileage had dropped due to the DPF.

My point wasn't to ask why I got the CEL and for suggestions to keep this from happening again - that is obviously interesting to me but has been discussed a lot. When I searched the forum for help, it appeared that there has been a lot of discussion about this topic including the option of cleaning the DPF vs replacing the whole system, but I couldn't find any account of someone actually having the cleaning done. It took me a while to figure out where to go and confirm that this process included both a muffler shop and a DPF cleaning shop. That now makes more sense as their business is nearly all big rigs with DPFs designed for easy removal. The shop I went to had never done a Colorado but was confident that they could figure it out. It felt like a gamble to me, but I was willing to take that chance. The dealer diagnosed the problem and immediately recommended I replace most of the exhaust system for around $2k which sounded typical from reading this forum. I told them I was going to go the cleaning route and they were curious about that but thought it sounded like a good idea and were supportive.

In retrospect I wish I had done a little more verification like you suggest and verifying that my regens had been happening regularly. Priorities change a bit when you are in a blizzard cycle, have an upcoming trip, and are swamped with unexpected work.
My first thought is how long did it stay at 21 mpg, could this have been a regen? It might be worth you getting a OBDii interface and an application (or a banks i-Dash gauge) so you can monitor soot level in the DPF and the status of your regens. This might shed some light on whats going on.
 

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Good points. My truck is a 2019 with 76k miles. No tune or deletion. It has lived mostly in Utah and Idaho so it's seen temps ranging from -22 to 107 deg F. Most of my driving has been on the highway (~45mph ave speed since new), I've towed several thousand miles, mostly with a 1800 lb trailer and maybe 500 easy miles with a 5k lb trailer and I never, ever idle it for more than about a minute. About the time the CEL came on, my mileage on a trip that I do often dropped from about 26 mpg to 21, but I was also in a fair bit of snow and cold temps. I didn't drive it long enough in that state to be confident that mileage had dropped due to the DPF.

My point wasn't to ask why I got the CEL and for suggestions to keep this from happening again - that is obviously interesting to me but has been discussed a lot. When I searched the forum for help, it appeared that there has been a lot of discussion about this topic including the option of cleaning the DPF vs replacing the whole system, but I couldn't find any account of someone actually having the cleaning done. It took me a while to figure out where to go and confirm that this process included both a muffler shop and a DPF cleaning shop. That now makes more sense as their business is nearly all big rigs with DPFs designed for easy removal. The shop I went to had never done a Colorado but was confident that they could figure it out. It felt like a gamble to me, but I was willing to take that chance. The dealer diagnosed the problem and immediately recommended I replace most of the exhaust system for around $2k which sounded typical from reading this forum. I told them I was going to go the cleaning route and they were curious about that but thought it sounded like a good idea and were supportive.

In retrospect I wish I had done a little more verification like you suggest and verifying that my regens had been happening regularly. Priorities change a bit when you are in a blizzard cycle, have an upcoming trip, and are swamped with unexpected work.
Keep in mind there are two different reasons why a dpf will get clogged first is soot and is the more common one (I would assume this is you because your mileage is so low) the second is ash but typically happens only after 150k or more miles. The first is the one the shops can clean or there are solvents and sprayers you can buy online to try first that you don’t have to remove the system you remove the pressure sensor and spray through there. I am surprised your system needs this considering you drive mostly highway miles, regens should take care of this unless your truck isn’t regening properly. The second clog is inevitable over time you will notice the time between regens gets shorter, this is because when you burn off soot what’s left over is ash which cannot be desolved by most solvents. At this point you either need to replace the dpf or remove and clean with Hydrochloric acid. This will dissolve the ash but too concentrated at you will destroy the metal. There’s a good YouTube video of a guy doing this
 

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I have seen some talk on the forum about DPF cleaning but haven't seen anything from anyone who actually had it done. My dealer recommended replacing most of the exhaust system after diagnosing a CEL as clogged DPF. The dealer said there was nothing wrong with the regens - I haven't hooked up the OBD yet to verify. The truck still ran fine but the mileage seemed to drop off a bit. I chose to clean the DPF instead. I found several local places that would clean the DPF (I live in Salt Lake City) but they all required the DPF to be taken off by someone else and delivered to them. I had a muffler shop remove the DPF and catalytic converter (the shop that did the cleaning strongly urged me to do both) and carried them to the cleaning shop. They cut both open, cooked them both overnight at around 1200 deg, and then did a solvent cleaning. They didn't have a way to measure the change in flow resistance (didn't fit in their testing equipment) but said that subjectively they both seemed to flow much better. The muffler shop reinstalled everything and reset the sensors and now there is no CEL. I haven't driven it enough to see if the mileage changed. So far it seems like this has worked well. It was a minor hassle running parts around but I saved about $1000 (total cost was $240 for the remove/replace and $811 for cleaning both). Both shops said they should be able to do this several times before the R&R and cutting the exhaust off and the cans open became too hard.

The muffler shop said they normally only see DPFs needing cleaning on trucks so clogged that they barely run and suggested if this happens again to do a forced regen or 2 to see if that works.

Curious to hear any criticism or thoughts on this. And hoping this info can help others.
I have a 2021 chevy colorado z71 with the 2.8 with about 71k miles. I also have this issue, as i was driving down the fwy I noticed my cel light had came on. I took it to autozone to use their scanner and it came out with cel code p0422 as a low catalyst efficiency. I took it to the dealer but it was already out of warranty, i was only covered if it was a bad catalytic converter , but they said my issue is with the dpf system and recommend to replace which is about $3,300. I haven't experienced any loss of power yet nor any reduced speed warnings. I am tempted to drive it a bit longer as is hoping that it clears. If that doesn't work then I am leaning towards the filter cleaning method. Also the lady at the dealer said that my truck doesn't have a catalytic converter, not sure if this is true or not?
 

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I have a 2021 chevy colorado z71 with the 2.8 with about 71k miles. I also have this issue, as i was driving down the fwy I noticed my cel light had came on. I took it to autozone to use their scanner and it came out with cel code p0422 as a low catalyst efficiency. I took it to the dealer but it was already out of warranty, i was only covered if it was a bad catalytic converter , but they said my issue is with the dpf system and recommend to replace which is about $3,300. I haven't experienced any loss of power yet nor any reduced speed warnings. I am tempted to drive it a bit longer as is hoping that it clears. If that doesn't work then I am leaning towards the filter cleaning method. Also the lady at the dealer said that my truck doesn't have a catalytic converter, not sure if this is true or not?
Your truck has three parts to the exhaust system first is bolted to turbo outlet it’s called a DOC, it’s basically a diesel version of a catalytic converter, next is the SCR (selective reductive catalyst) this is the first cylinder looking thing underneath after the pipe turns horizontal, this is where your DEF fluid is injected to lower NOx gasses. The last cylinder is the DFP, you will see two pressure sensors mounted on either side and fuel rail going just upstream Of the DPF this is where diesel is injected to “regen” the DPF. You can try one of the oftermarket dpf spray cleaners that you spray into the hole where the pressure sensor is. At such low mileage you most likely have soot blockage. What’s troubling is these dealers just want to slap a new DPF on without troubleshooting why it’s getting clogged in the first place.
 

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Your truck has three parts to the exhaust system first is bolted to turbo outlet it’s called a DOC, it’s basically a diesel version of a catalytic converter, next is the SCR (selective reductive catalyst) this is the first cylinder looking thing underneath after the pipe turns horizontal, this is where your DEF fluid is injected to lower NOx gasses. The last cylinder is the DFP, you will see two pressure sensors mounted on either side and fuel rail going just upstream Of the DPF this is where diesel is injected to “regen” the DPF. You can try one of the oftermarket dpf spray cleaners that you spray into the hole where the pressure sensor is. At such low mileage you most likely have soot blockage. What’s troubling is these dealers just want to slap a new DPF on without troubleshooting why it’s getting clogged in the first place.
Thank you for the quick response, do you know the name of the spray by any chance? I went to the local auto parts but I didn't see any sprays related to dpf. I only found a fuel additive made by lucas that helps clear clogged filters and injectors
 

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Thank you for the quick response, do you know the name of the spray by any chance? I went to the local auto parts but I didn't see any sprays related to dpf. I only found a fuel additive made by lucas that helps clear clogged filters and injectors
 

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Discussion Starter · #10 ·
Anyone on here tried this or have any sense of how effective it is?
 

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Discussion Starter · #11 ·
Follow up observation and questions:
About 500 mi after my DPF cleaning, I got an email message that I had an emission system issue requiring attention. No CEL. I checked codes and found aP24B1 code (Particulate Matter Sensor Circuit High Voltage) and the following advice via the Google: Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector's pins. Easy enough, although it will involve rolling around the the snow underneath my truck at the moment (yeah, I need a bigger shop to pull it into). Any other thoughts on that aside from poking around and looking for visible damage? There is no indication from the truck that anything is wrong - I would not have known about this if not for the email from Chevrolet.

Related question: I'm trying to verify that I'm getting regens regularly. I have a Veepeak OBDCheck BLE scan tool and the OBD Fusion app. I've searched through the app and found the average miles between regens (about 400 mi) but can't find the time of last regen or any way to manually trigger one. Does anyone know if I missing something? Or if that info is not available with my scan tool and app?
Thanks
 

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Follow up observation and questions:
About 500 mi after my DPF cleaning, I got an email message that I had an emission system issue requiring attention. No CEL. I checked codes and found aP24B1 code (Particulate Matter Sensor Circuit High Voltage) and the following advice via the Google: Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector's pins. Easy enough, although it will involve rolling around the the snow underneath my truck at the moment (yeah, I need a bigger shop to pull it into). Any other thoughts on that aside from poking around and looking for visible damage? There is no indication from the truck that anything is wrong - I would not have known about this if not for the email from Chevrolet.

Related question: I'm trying to verify that I'm getting regens regularly. I have a Veepeak OBDCheck BLE scan tool and the OBD Fusion app. I've searched through the app and found the average miles between regens (about 400 mi) but can't find the time of last regen or any way to manually trigger one. Does anyone know if I missing something? Or if that info is not available with my scan tool and app?
Thanks
The only way to know is by watching your instant fuel economy. It will drop 5 to 7 mpg during the regen. Some of the OBDii devices will tell you when it's in an active regen. I use a banks i-Dash gauge and that will tell you. I have never seen anything dated in the list of things to monitor. You can see how many average miles between a regen, how many miles driven since the last regen completed and current soot % in the dpf. Since all this data is running down the data buss I would tend to think you should be able to monitor that with Fusion as well.
 
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