scr warmup

[Mudflap77]

(05-11-2023 )Rawze Wrote:  regen history looks ok to me at a glance.

What do you mean you don't understand?.. Those SCR and DPF canisters cannot function properly if they fall much below about 450-F or so. IT IS ABSOLUTELY NORMAL FOR THE ENGINE TO JUMP BACK AND FOURTH IN OPERATING MODES TO REGULATE THOSE AFTERTREATMENT COMPONENT TEMPS PROPERLY! ... They cannot convert the exhaust gasses .. and therefore it will not pass an EPA inspection unless those cans stay hot all the time.

THAT IS WHAT IT IS DESIGNED TO DO... Keep the temperatures up and within operating range so that they can convert the exh. gases properly.

-= Sounds to me like you are worried about it actually doing its proper job, and your regen history looks like it is doing its thing as well.

If you want it to switch modes less often, then I would suggest you invest in an exhaust wrap to help keep the temps up.

What I don't understand is why it will going into scr warmup at low idle go inactive at 280f you start driving and it will remain inactive. Scr outlet can be up to 400-500 degrees when stopping at a light, engine at idle for 10 seconds or so it goes into scr warmup start driving it will stay in warmup for 30 to 40 minutes with scr outlet temp over 500f.
Get back to the yard 10 seconds at low idle into scr warmup. Let it do its thing until it's inactive and put it on high idle and bring it back to low idle it will go back to scr warmup.
It seems like it goes into scr warmup everytime it spends10sec at low idle regardless of temp.

If it is doing what's its supposed to when it's supposed to, Perhaps its shedding light onto another problem that the symptoms only show up when in scr warm up. That's what I'm trying to figure out here.
That's my main concern is the way it runs while driving in the warmup mode. Over boosting up to 40psi and chaulfing if not careful when shifting while in warmup mode and only in warmup.

[Rawze]

(05-15-2023 )Mudflap77 Wrote:  .... Over boosting up to 40psi and chaulfing if not careful when shifting while in warmup mode and only in warmup.

That is an engine issue .. not an operating mode issue.

Partially clogged or after-garbage EGR cooler, ... maybe partially clogged egr piping, maybe bad (or garbage after-market) egr pressure sensor.. or just maybe.. the program itself does not match the engine ser# or needs an update.

For all anyone knows.. the turbo itself could have been replaced at some point with the wrong model.

Its anyone's guess... however ...

Turbo over-spooling and chuffing is usually an engine problem associated with the EGR system not breathing properly and not typically an scr issue ... however a partially blocked up exhaust system can contributed towards the overall issue, making it worse.
this post should help... http://rawze.com/forums/showthread.php?t...8#pid22458

[Mudflap77]

Thanks Rawze,
That's was I was trying to get figured out.
What has been throwing me off is that it only happens during scr warm up.
Egr cooler is amazingly still original and is clear no blockage, was cleaned out last year when I was having aftertreatment issues, I visually checked it and a the piping a few weeks ago. I'll take a closer look at the sensors that were replaced, I have gotten a aftermarket sensor in cummins packaging before.
Cummins program matches engine serial #. As far as I know there hasn't been any new updates since it was updated last.
Turbo and actuator was replaced last year due to there being a tough spot when moving the ring arm. Will have to look into the turbo model.
Thanks agian Rawze and Jim T

[onebadapple]

Hey Mudflap77 Had and now again having a similar problem. Search Rawze: “No lights no codes”. Had a cracked DOC under the heat shield. Fine for a year+. IT’S BACK! How did you fix it?

[JimT]

Back when I had a functional system I was experiencing the issue of frequent SCR warmups. Nearly any time the engine dropped back down to idle for more then (i'm guessing here) about 20-30 seconds it would kick into warmup mode. Initially I thought it was DPF regens (which I was having frequently because my DOC and DPF were shot) but after connecting Insite a few times I was able to see that it was actually SCR warmup. This led me to try replacing my DEF doser. That didn't help. My next suspect was the Outlet NOx sensor -- in range but higher than expected NOx values can trigger the SCR warmup at idle. Never got around to testing that as my DOC/DPF became non-functional about the same time and were subsequently permanently retired. I read many sources, both forums and official bulletins, that pointed to recurring failures of the Outlet NOx sensor, especially on the earlier 2010-2013 systems with the long winding undercarriage exhausts. Something about the placement of the sensor, they had a campaign or something about installing a splash shield. Also, it was common for people to find that when the sensor failed it would report inaccurate but still in-bound values making it hard to spot.

Anyway, this was late 2019 to early 2020 when I was researching this, so everything above is pulled from my memory. My point here is that something is signalling to the ECM that it needs to enter SCR warmup. It could be anything, but I would start by really looking closely at all the sensors. Hook up Insite, pull up data monitor with the relevant items and go for a drive. Look for any abnormalities, even those that might still be valid values. Also, inspect the SCR decomp tube and the DEF doser valve. Look for leaks and/or DEF buildup. Also, if temps coming OUT of the DPF are too low that could be cause the issue too. That could be caused by poorly functioning DOC, exhaust leaks, leaking DPF doser / 7th injector, or malfunctioning EGR valve. Basically anything that could lead to lower DPF temps.

Something else to consider, some of the values are actually calculated by the ECM instead of measured by a sensor. It's possible that the calculated value is wrong due to other sensors or assumptions that the ECM is making which, for whatever reason, are inaccurate. For instance avalid but inaccurate IMAP reading could throw off ECM calculations about what it expects the engine to produce during combustion, then later downstream when measurements are taken they don't fall into the range the ECM expects. This is another reason why regular EGR tuneups are so important. There is a delicate balance that must be maintained from air and fuel intake all the way to the end of the exhaust pipe. An issue anywhere in the process could disrupt this balance of circular dependencies.

[Rawze]

Actually, it is quite normal for the engine to jump back and fourth between its egr+ modes and one of its aftertreatment warm-up modes. It has to maintain 500-F degrees at the DPF/SCR, etc.. and it can only do this by jumping into a warm-up mode as those cans drop below about 450-F or so, and they cool off.

The idle alone in the EGR+ operating modes is not enough heat to keep the SCR/DPF temps under there up .. so it jumps as needed into a warm-up cycle to get them back where they need to be. It also, often, does this going down the roads every few mins, depending on weather.

If you want it to cycle less often, then an exhaust wrap to keep everything under there much warmer would help a lot.

As far as it cycling more than normal,.. it could be caused by many tings including an egr valve sticking open, leaky exhaust piping, one of the temp sensors under the truck not reading correctly, etc.

[onebadapple]

(08-25-2023 )JimT Wrote:  Back when I had a functional system I was experiencing the issue of frequent SCR warmups. Nearly any time the engine dropped back down to idle for more then (i'm guessing here) about 20-30 seconds it would kick into warmup mode. Initially I thought it was DPF regens (which I was having frequently because my DOC and DPF were shot) but after connecting Insite a few times I was able to see that it was actually SCR warmup. This led me to try replacing my DEF doser. That didn't help. My next suspect was the Outlet NOx sensor -- in range but higher than expected NOx values can trigger the SCR warmup at idle. Never got around to testing that as my DOC/DPF became non-functional about the same time and were subsequently permanently retired. I read many sources, both forums and official bulletins, that pointed to recurring failures of the Outlet NOx sensor, especially on the earlier 2010-2013 systems with the long winding undercarriage exhausts. Something about the placement of the sensor, they had a campaign or something about installing a splash shield. Also, it was common for people to find that when the sensor failed it would report inaccurate but still in-bound values making it hard to spot.

Anyway, this was late 2019 to early 2020 when I was researching this, so everything above is pulled from my memory. My point here is that something is signalling to the ECM that it needs to enter SCR warmup. It could be anything, but I would start by really looking closely at all the sensors. Hook up Insite, pull up data monitor with the relevant items and go for a drive. Look for any abnormalities, even those that might still be valid values. Also, inspect the SCR decomp tube and the DEF doser valve. Look for leaks and/or DEF buildup. Also, if temps coming OUT of the DPF are too low that could be cause the issue too. That could be caused by poorly functioning DOC, exhaust leaks, leaking DPF doser / 7th injector, or malfunctioning EGR valve. Basically anything that could lead to lower DPF temps.

Something else to consider, some of the values are actually calculated by the ECM instead of measured by a sensor. It's possible that the calculated value is wrong due to other sensors or assumptions that the ECM is making which, for whatever reason, are inaccurate. For instance avalid but inaccurate IMAP reading could throw off ECM calculations about what it expects the engine to produce during combustion, then later downstream when measurements are taken they don't fall into the range the ECM expects. This is another reason why regular EGR tuneups are so important. There is a delicate balance that must be maintained from air and fuel intake all the way to the end of the exhaust pipe. An issue anywhere in the process could disrupt this balance of circular dependencies.

Hello JimT! The SCR warm up mode to keep things hot enough makes sense, however, when my ‘15 ISX sticks in the SCR warm up for what appears to be no reason, I can temporarily turn it off while parked with the cruise control, let it cool a bit, then turn the engine off for 15 minutes. Restart it and it’s fine for a day or two. Any input?

[JimT]

(08-25-2023 )Rawze Wrote:  Actually, it is quite normal for the engine to jump back and fourth between its egr+ modes and one of its aftertreatment warm-up modes. It has to maintain 500-F degrees at the DPF/SCR, etc.. and it can only do this by jumping into a warm-up mode as those cans drop below about 450-F or so, and they cool off.

The idle alone in the EGR+ operating modes is not enough heat to keep the SCR/DPF temps under there up .. so it jumps as needed into a warm-up cycle to get them back where they need to be. It also, often, does this going down the roads every few mins, depending on weather.

If you want it to cycle less often, then an exhaust wrap to keep everything under there much warmer would help a lot.

As far as it cycling more than normal,.. it could be caused by many things including an egr valve sticking open, leaky exhaust piping, one of the temp sensors under the truck not reading correctly, etc.

I should clarify, when I speak of SCR warmup cycling too often, I mean no matter how long you've been driving or how much stop and go you are doing every time you stop at a red light or stop sign for more than 20-30 seconds the system would kick into SCR Warmup bringing the engine up to about 1000 RPM and spooling up the turbo. I always mistook it for an ongoing DPF regen until I monitored it with Insite. Also, these occurrences I reference are outside of what has been observed as normal operation over months or years of driving that same vehicle. I've personally seen the issue crop up in 2 different trucks (prior to also experiencing it in my own truck) I drove as a company driver, both I had been in since they were new and were daycabs used for distance and city driving. As to the company trucks I can only assume that driver (myself and others) and maintenance neglect (mostly Ryder) of the aftertreatment systems along with the large amount of NYC stop and go contributed to the problem. But the point is there's normal system operation and then there's excessive occurrences which is to what I'm referring.

Slightly unrelated, but the SCR warmup and DPF regens durring stop and go driving are the only reason I liked, back then, having an automated manual. It was always annoying getting ready to take off from a stop when the system would kick in and spike your RPMs without your input. I can't imagine the extra clutch wear from repeatedly having to get 80K moving from a stop while the engine is spinning at 1000 RPM.

onebadapple: Sorry, I don't have any answers for you other then test and troubleshoot. First thing hook up Insite and pull up data monitor to verify exactly which mode the engine is in when you experience this. While I can't say for sure, what you describe could be part of a Regen your interrupting and it takes a day or two before the levels once again cause the system to Regen.

[Mudflap77]

Ok!!!! After a long, painful, irritating, head banging against the wall process I finally figured out my issue. And it was so simple, stupid and frustrating on so many levels.
The big issue, (trumpets) the reman turbo installed came with the WRONG turbo intake temp sensor in it. The culprit was a short probe sensor that was basicly reading the turbo intake house temp and not the flow of air.
There is no turbo intake temp sensor part # in Quickserve. Searching through all sensors you will come across 1 sensor simply labeled temp sensor. looking up that p/n on shop cummins its labeled as oil/coolant sensor. That appears to be the sensor that came in the turbo. The cummins parts guy had to find a parts breakdown for the turbo that only cummins has access to to find the proper p/n.

Since changing that sensor a couple of days ago the motor general only goes into SCR warmup at start up and for a very brief period when idling warm. The motor isn't trying to over produce heat now. Oil and coolant temps are far more stable when driving and pulling a hill.
Turbo pressure is far easier to control with the throttle in SCR warmup, meaning its easier to maintain say 20psi while accelerating whereas before the turbo wanted boost right up.
While in SCR warm the turbo will still boost up to 40psi but no longer chulfs at that higher boost. Agian this only ever happens in SCR warmup.
I don't know if there will be an improvement in fuel mileage yet as I real only had 1 day with a decent load on and it decided to do a regen while i was in some pretty good hills.
Many thanks to this forum and Rawze for trying to help me sort this thing out