938M Regen data

[Innocent bystander]

S# J3R

Hrs=6000

Looking for any helpful regen data-Temps pressures ect during a regen. Has to be on 938M or Similar with cat "Clean Emissions Module" sealed unit without ARD head.

Main problem= Does not want to burn off soot. No Fault code or event codes, however high soot load continues to pop up.

Passes all regen tests.

Fails to complete regen with Et error 1173 (Not fault code) stating soot reduction to low.

 

[Island_catguy]

It’s probably clogged. Pull the DOC and check if the face is plugged. I’ve had good success back flushing with hot water and a mild degreaser. All systems are the same, you want the inlet and outlet temps close to each other by the end of the regen, and differential pressure to be close to nothing. This shows good flow through the CEM.

What soot percent are you at before and after the regen? How long did you regen before it failed? Have you changed the oil? The dirtier the oil, the more it burns soot.

 

[Innocent bystander]

Current oil change
Sealed unit, can not disassemble and inspect,
Removed and had cleaned= Soot was at 20% at clean install. Seems when sot load reached level requiring a regen then would not reduce soot.
This system does not use or have DPF differential pressure sensor.
How long before regen failed? 20-30 min.
Soot stays around 110-115 sometimes will go down to 95, but goes UP to 110-115 during a regen. If I perform aftertreatment recovery procedure it will go down to 95 but Service regen seems to make it go up
Looking for turbo boost pressure during regen? I have "0" Not sure if it should have any.

 

[Island_catguy]

When you had the unit cleaned, did you reset it? Most trucks have a setting for when you clean or put on a new CEM. I’m not sure about your machine. Do you have the option for a delete or is the customer worried about the epa? It looks like he will be buying a new CEM to fix the issue now. Or you can hollow that one out and delete it.

 

[Island_catguy]

Current oil change
Sealed unit, can not disassemble and inspect,
Removed and had cleaned= Soot was at 20% at clean install. Seems when sot load reached level requiring a regen then would not reduce soot.
This system does not use or have DPF differential pressure sensor.
How long before regen failed? 20-30 min.
Soot stays around 110-115 sometimes will go down to 95, but goes UP to 110-115 during a regen. If I perform aftertreatment recovery procedure it will go down to 95 but Service regen seems to make it go up
Looking for turbo boost pressure during regen? I have "0" Not sure if it should have any.

And most of the units I’ve needed to regen will be at 98%, and drop close to zero before an hour. The only times I e had your identical issue was on the older dpf units without def, when the turbo seals failed and dumped oil into the exhaust and blocked the dpf. You can always check for charge air leaks as well if you aren’t seeing boost. If a boot is torn, it can throw the turbo off balance and cause oil to leak from the seals inside the turbo shaft. You can stick a camera down inside and check to see if the CEM is getting blocked. I know it’s a sealed unit, but in reverse flush them all the time. Just boil a big pot of water and use a mild degreaser. When def injectors used to fail and block the scr, we’d use this method and then let it dry out over night before putting it back together. It’s worth a shot. Most of those sealed units are well over 5k.

 

[ahart]

To the OP, I think we need to back up on this one, do not take the advice of replacing the CEM just yet and definitely don’t go busting it out for a delete as you will lose any dealer support in the future. One thing that should probably be checked is the soot sensor. You’ll need the attenuator to accomplish that. Past that, need to check the exhaust back pressure valve for correct function, also need to check the EGR valve for proper function. Checking EGR cooler and tubes for plugging should also be done. What temps are you seeing on a regen? Should be upwards of 800-1000 degrees or somewhere in that vicinity.

 

[Innocent bystander]

To the OP, I think we need to back up on this one, do not take the advice of replacing the CEM just yet and definitely don’t go busting it out for a delete as you will lose any dealer support in the future. One thing that should probably be checked is the soot sensor. You’ll need the attenuator to accomplish that. Past that, need to check the exhaust back pressure valve for correct function, also need to check the EGR valve for proper function. Checking EGR cooler and tubes for plugging should also be done. What temps are you seeing on a regen? Should be upwards of 800-1000 degrees or somewhere in that vicinity.

No thoughts of delete.....yet. I really want to figure out why its not burning off.
As far as replacing, it sure seems like DOC is not reacting to the added fuel and creating enough heat. During a regen it only gets to around 650 deg. performing Aft, sys function test went up over 700Deg pretty quick and passes. performing Aft, recovery procedure DPF in temp 825 deg and passes. Performing aft recovery procedure temp gets around 925. Even with DPF temp over 900 for 45 min during Recovery procedure soot only down to 95% then just goes for ever trying to drop soot below i think 70 but never does. I have replaced both soot ant. sensors but dont have the atteneuator to run the test. The EGR and ex back pressure valve appear to be working but not sure how to tell if function correct.

 

[Island_catguy]

No thoughts of delete.....yet. I really want to figure out why its not burning off.
As far as replacing, it sure seems like DOC is not reacting to the added fuel and creating enough heat. During a regen it only gets to around 650 deg. performing Aft, sys function test went up over 700Deg pretty quick and passes. performing Aft, recovery procedure DPF in temp 825 deg and passes. Performing aft recovery procedure temp gets around 925. Even with DPF temp over 900 for 45 min during Recovery procedure soot only down to 95% then just goes for ever trying to drop soot below i think 70 but never does. I have replaced both soot ant. sensors but dont have the atteneuator to run the test. The EGR and ex back pressure valve appear to be working but not sure how to tell if

No thoughts of delete.....yet. I really want to figure out why its not burning off.
As far as replacing, it sure seems like DOC is not reacting to the added fuel and creating enough heat. During a regen it only gets to around 650 deg. performing Aft, sys function test went up over 700Deg pretty quick and passes. performing Aft, recovery procedure DPF in temp 825 deg and passes. Performing aft recovery procedure temp gets around 925. Even with DPF temp over 900 for 45 min during Recovery procedure soot only down to 95% then just goes for ever trying to drop soot below i think 70 but never does. I have replaced both soot ant. sensors but dont have the atteneuator to run the test. The EGR and ex back pressure valve appear to be working but not sure how to tell if function correct

No thoughts of delete.....yet. I really want to figure out why its not burning off.
As far as replacing, it sure seems like DOC is not reacting to the added fuel and creating enough heat. During a regen it only gets to around 650 deg. performing Aft, sys function test went up over 700Deg pretty quick and passes. performing Aft, recovery procedure DPF in temp 825 deg and passes. Performing aft recovery procedure temp gets around 925. Even with DPF temp over 900 for 45 min during Recovery procedure soot only down to 95% then just goes for ever trying to drop soot below i think 70 but never does. I have replaced both soot ant. sensors but dont have the atteneuator to run the test. The EGR and ex back pressure valve appear to be working but not sure how to tell if function correct.

Yeah cat isn’t the friendliest when it comes to showing data while performing regens. The egr and back pressure valves are testing in the beginning of the regen and after recovery procedure. It’s will say “checking back pressure” or something similar. I would like to see temps closer to 1000. Esp after 45 mins. You will need to at least pull the inlet pipe off and stick a camera down inside. I’d still pull the assembly off and backwards flush first. We usually take a giant pot with a propane stove and do a few rounds. Never know, the people you sent it out to be cleaned could have done a bad job.

 

[ahart]

it sure seems like DOC is not reacting to the added fuel and creating enough heat.

This isn’t how this aftertreatment system works. No fuel is injected into the CEM on these. They use the EBPV to create a restriction, which in turn, raises the exhaust temperatures in the CEM. As far as testing these two components goes, you have to remove them from the machine, run the air motor valves test and physically watch them go through the cycle. Low temperature in a CEM is almost always due to improper flow. Soot sensor needs to be verified, EGR system need to be checked and confirmed to be clear and functioning properly, etc.

Yeah cat isn’t the friendliest when it comes to showing data while performing regens.

As far as this goes, you can see as much data during a regen as the ecm contains but you will likely have to run a data log while the regen is running to see it. The need to put a shadow mode in the programming where you can monitor the status screen during a service test but that’s not coming any time soon.

 

[Innocent bystander]

This isn’t how this aftertreatment system works. No fuel is injected into the CEM on these. They use the EBPV to create a restriction, which in turn, raises the exhaust temperatures in the CEM. As far as testing these two components goes, you have to remove them from the machine, run the air motor valves test and physically watch them go through the cycle. Low temperature in a CEM is almost always due to improper flow. Soot sensor needs to be verified, EGR system need to be checked and confirmed to be clear and functioning properly, etc.


As far as this goes, you can see as much data during a regen as the ecm contains but you will likely have to run a data log while the regen is running to see it. The need to put a shadow mode in the programming where you can monitor the status screen during a service test but that’s not coming any time soon.

You are correct that no fuel is injector like a 7th injector however it does use post injection to introduce fuel into the exhaust that reaches the DOC to create heat in addition to the back pressure(at least thats how I understand it). Another way to monitor all data during a regen is to start a regen, disconnect com-link from laptop, back out of regen screen then reconnect com-link and then you can open data monitoring. I dont really care to do it that way but it works.

Watch this video I found today. This is exactly where I am at and it took an ECM to fix it.

 

[Island_catguy]

You are correct that no fuel is injector like a 7th injector however it does use post injection to introduce fuel into the exhaust that reaches the DOC to create heat in addition to the back pressure(at least thats how I understand it). Another way to monitor all data during a regen is to start a regen, disconnect com-link from laptop, back out of regen screen then reconnect com-link and then you can open data monitoring. I dont really care to do it that way but it works.

Watch this video I found today. This is exactly where I am at and it took an ECM to fix it.

Bro that sucks. I wish you had a test ecm to confirm. Looks exactly like what you are going through.

 

[ahart]

You are correct that no fuel is injector like a 7th injector however it does use post injection to introduce fuel into the exhaust that reaches the DOC to create heat in addition to the back pressure(at least thats how I understand it)

Any chance you could provide the data to back this up? I’m new to this regen stuff and just trying to understand how it all works.

 

[Island_catguy]

You are correct that no fuel is injector like a 7th injector however it does use post injection to introduce fuel into the exhaust that reaches the DOC to create heat in addition to the back pressure(at least thats how I understand it). Another way to monitor all data during a regen is to start a regen, disconnect com-link from laptop, back out of regen screen then reconnect com-link and then you can open data monitoring. I dont really care to do it that way but it works.

Watch this video I found today. This is exactly where I am at and it took an ECM to fix it.

I never saw them try to flash to the latest calibration for the ecm either. They just went brand new. You might wanna try and see if you can flash to the latest calibrations for both the ecm and dcu.

 

[Innocent bystander]

Any chance you could provide the data to back this up? I’m new to this regen stuff and just trying to understand how it all works.

It is common practice on some other engines to use post injection( open injectors when ex valve is open) instead of using a down stream injector. I was talking to a cat tech that confirmed c7.1 does. I may have read it somewhere else also, if I find it I will post it.

 

[Innocent bystander]

I never saw them try to flash to the latest calibration for the ecm either. They just went brand new. You might wanna try and see if you can flash to the latest calibrations for both the ecm and dcu.

I thought the same, he did not show it but possibly did reflash with latest calibration, being a dealer I will assume they did that first. I did recalibrate to latest with same results, I also reset soot load twice I think with same results....ordered new ECM....we will see!