# Help diagnose bucking during regens



## Barefeet (Jan 1, 2014)

This started after the recall last December to replace nox sensor and flash ecm. During regens the car bucks and runs rough, it will usually throw a CEL (2453 pressure sensor) I cleared the codes myself a few times and tolerated the rough running. In June I took it in for the CEL 2453 and they re-flashed the ECM. The next time it came on they changed the pressure sensor, but that did not help. I took it back and told them I was tired of this and to fix it. They gave me a courtesy vehicle (brand new Malibu) to drive. Three days later they said the plenum to the turbo was leaking so they replaced it. Today during the regen the car still is bucking and running rough, no CEL yet but I expect it will come on soon. I told them about the broken exhaust bolt that had caused a previous problem. They said they checked for leaks in the exhaust. The car has 74k miles on it so the warranty will not cover this. I am taking it back this Tuesday and they will throw more parts at it I am afraid how much this will cost. Any suggestions what to look for?


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## MRO1791 (Sep 2, 2016)

How bad is the bucking? Both my CTDs do minor fluctuations during regen. My Cummins is by far more severe, especially if in Cruise and going downhill. Some fluctuating is normal, yours seems more than that. Induction side, and exhaust side leaks could contribute, but seems you have looked at that already. Do you have the most recent recall?? 

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## Barefeet (Jan 1, 2014)

They re-flashed the ECM in June. It's especially bad when driving 20 to 40 mph on a slight uphill. It is bad enough that my wife complains and I am embarrassed to have anyone riding with me. I had the service manager ride with me so he could see what it is doing. The car never did this until last December at about 53k. and it started right after I took it in for the recall that they had back then.


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## Spoolin6Spd (Jun 19, 2017)

Sure is too bad diesels come with all this crap these days....  

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## VtTD (Nov 5, 2013)

Edit: Didn't read the rough running engine and CEL you mentioned. That does not seem normal. Mine is as described below, but bucking only. I have been getting a CEL lately during regens, but it's the NOX issue (always sensor 1 and/or 2 codes).

Yeah mine was fine originally then started this problem a few years ago. Exactly as you describe. Also at rock bottom RPMs at higher speeds (ie 50, 55mph - although not as bad as the 20-40mph range you indicate). Dealer didn't know. Didn't get any real answers here. I think it's common though. It's annoying, but has not seemed to get any worse since it started. I'd just leave it if I were you. If this was a higher production car there would probably be a more straightforward answer as to why it's happening.


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## MRO1791 (Sep 2, 2016)

Barefeet said:


> They re-flashed the ECM in June. It's especially bad when driving 20 to 40 mph on a slight uphill. It is bad enough that my wife complains and I am embarrassed to have anyone riding with me. I had the service manager ride with me so he could see what it is doing. The car never did this until last December at about 53k. and it started right after I took it in for the recall that they had back then.


I'd make sure you get the newest recall, the prior one specifically was suspended since it was causing problems. I have the newest recall flash on one of mine, it's been running fine, perhaps even a slight MPG increase. I personally did not have issues with the prior suspended recall on either car, one of mine is still running it, but I'll be getting it also updated soon. It is possible that the reflash will make things better for you, and being a recall, it's no cost. Good luck, and if you do it, let is know if it helped.

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## MRO1791 (Sep 2, 2016)

Spoolin6Spd said:


> Sure is too bad diesels come with all this crap these days....
> 
> Sent from my SM-G935V using Tapatalk


Yep, thanks to the EPA and junk science for the most part..

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## Barefeet (Jan 1, 2014)

I'm not sure if there is a newer ECM flash since June, but the car goes back in a couple of days I will ask them. The code 2453 which I get during every regen is DPF pressure sensor part number 55570092. The service dept. says it tested non responsive. The new one they put in did not help.


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## dougc905 (May 24, 2015)

Barefeet said:


> The service dept. says it tested non responsive. The new one they put in did not help.


Maybe the port on the ecu that the sensor is attached to is bad => bad ecu


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## theonlypheonix (Oct 8, 2015)

Barefeet said:


> I'm not sure if there is a newer ECM flash since June, but the car goes back in a couple of days I will ask them. The code 2453 which I get during every regen is DPF pressure sensor part number 55570092. The service dept. says it tested non responsive. The new one they put in did not help.


Confused... the new one did not help what? In fixing the bucking problem or with the test of the sensor responsiveness?

Along with the emission recall there is the NOX1 sensor replace, reprogramming and also a manual Regen, do you know whether everything was completed? I might suspect that, given the number of miles on the clock, maybe the EGR is is full of carbon and sticking but also the MAP sensor would probably need cleaning?


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## Barefeet (Jan 1, 2014)

The NOX 1 was replaced just before the recall. They said they now don't do the manual regen because when they re flash the ecm it memorizes the soot level. When I said replacing the sensor did not help I meant that the next regen was the same as before, lot of bucking and CEL came back on (code 2453) I took the car back today and they gave me the new Malibu courtesy vehicle. I did tell them to check the EGR. I expressed my concern that they would just throw parts at it and this was going to be expensive. They said that they are working with the engineers at Chevy and they would keep me informed. I wondered about the MAP sensor, you are probably right that it should be cleaned, however, I think they tend to replace parts rather than clean them.


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## MRO1791 (Sep 2, 2016)

Barefeet said:


> The NOX 1 was replaced just before the recall. They said they now don't do the manual regen because when they re flash the ecm it memorizes the soot level. When I said replacing the sensor did not help I meant that the next regen was the same as before, lot of bucking and CEL came back on (code 2453) I took the car back today and they gave me the new Malibu courtesy vehicle. I did tell them to check the EGR. I expressed my concern that they would just throw parts at it and this was going to be expensive. They said that they are working with the engineers at Chevy and they would keep me informed. I wondered about the MAP sensor, you are probably right that it should be cleaned, however, I think they tend to replace parts rather than clean them.


I'm calling BS on the dealership saying they don't do the manual Regen, it's on the recall notice as work to be performed, and reset of the fuel trim. If they didn't do it, that right there could be the problem. My dealership did the service regen with mine. Snipesy came up with a plug-in for the Torque app, I use that and can do my own service Regen. It's not difficult. I'd ask them again about this, and demand they do it, and reset the fuel trims. Good luck.

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## CruzeDan (May 17, 2015)

The instructions for the first recall do not say to do a manual regen. I didn't when I did mine, had no issues. When I did the recall for the recall I did a manual regen, as it was in the instructions that time. Again, no issues. As for the OP, there is another post about this topic on the forum. My car bucks rarely during regen, it happens occasionally at a certain speed, around 25, and a certain RPM. I haven't noticed it in quite a while. I think it is just a quirk of how they are performing the regen. Your car probably has additional issues though looking at the CEL and codes.


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## justin13703 (May 2, 2016)

Mine bucks during a regen too. It doesn't seem speed related, but more throttle position related. Under light throttle is when mine does it.

Best thing I can tell you, is when it starts bucking, run the absolute piss out of it. When I do this in mine I guess it makes the regen complete faster because of the higher heat and within a few minutes it's not doing it anymore. You're not going to get anywhere with the dealership. No one knows why they do it, and why some do and some don't.


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## Barefeet (Jan 1, 2014)

justin13703 said:


> Mine bucks during a regen too. It doesn't seem speed related, but more throttle position related. Under light throttle is when mine does it.
> 
> Best thing I can tell you, is when it starts bucking, run the absolute piss out of it. When I do this in mine I guess it makes the regen complete faster because of the higher heat and within a few minutes it's not doing it anymore. You're not going to get anywhere with the dealership. No one knows why they do it, and why some do and some don't.


Speed definitely helps, however , I don't want to do an extra 20 miles of expressway driving every 150 miles. They need to fix this problem. The car is still in the shop. l will post any results. Thanks for the suggestions


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## justin13703 (May 2, 2016)

Barefeet said:


> Speed definitely helps, however , I don't want to do an extra 20 miles of expressway driving every 150 miles. They need to fix this problem. The car is still in the shop. l will post any results. Thanks for the suggestions


I don't drive any extra distance. I just run it harder for the distance I'm going. Yeah it's a stupid issue that shouldn't happen but I personally don't want to spend money on this issue.

Something I notice, since I have an intake I can hear a lot more engine/turbo noise. When the car gets into one of these bucking fits, I can actually hear a small amount of compressor surge from the turbo. So maybe the throttle blade is involved somehow in this bucking issue.


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## Barefeet (Jan 1, 2014)

Keeping the RPMs up does disguise the rough running. I sometimes use the manual shift.


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## sailurman (Sep 29, 2016)

80K Miles. Have not had any bucking yet. And, I do a lot of around time driving.


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## LulzT1 (Aug 24, 2015)

Mine bucks during regen at low-er speeds (like up to 35mph), I'm usually on the highway so I don't notice it until I get caught up in traffic. I usually keep a good distance between me and the next car so I can coast between and minimize the bucking. As long as I don't get an CEL, I'll live with it haha at least you can work around it.

IMO, it got way worse after the most recent NOx recall and flash I did back in May. Not sure if anyone else noticed that.


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## Barefeet (Jan 1, 2014)

Update. After a week in the shop, Chevy engineers recommended replacing the "catalytic converter-GM (12659575). This was covered under warranty, the bill would have been $1743. The car did a regen yesterday and there was no change, it still runs rough and the CEL cane back on code 2354. I will take it back again.


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## justin13703 (May 2, 2016)

Barefeet said:


> Update. After a week in the shop, Chevy engineers recommended replacing the "catalytic converter-GM (12659575). This was covered under warranty, the bill would have been $1743. The car did a regen yesterday and there was no change, it still runs rough and the CEL cane back on code 2354. I will take it back again.


That doesn't even make sense to me why they would replace that.

Anyway, there is this kind of mystery behind the existence of a throttle blade on this engine as most diesels do not have one. The general conclusion that I've seen on here is that it must have something to do with the regen process. I know that I hear compressor surge/flutter when mine starts bucking during a regen. The only thing that I can think of that can cause this is the throttle blade closing for some reason. I wish I had a scanner tool to monitor this blade, but to me it seems like the bucking, at least on my car, is being caused by the throttle blade closing for some reason under certain throttle conditions.

I could be completely wrong, but thats what I was thinking.


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## Barefeet (Jan 1, 2014)

justin13703 said:


> That doesn't even make sense to me why they would replace that.
> 
> Anyway, there is this kind of mystery behind the existence of a throttle blade on this engine as most diesels do not have one. The general conclusion that I've seen on here is that it must have something to do with the regen process. I know that I hear compressor surge/flutter when mine starts bucking during a regen. The only thing that I can think of that can cause this is the throttle blade closing for some reason. I wish I had a scanner tool to monitor this blade, but to me it seems like the bucking, at least on my car, is being caused by the throttle blade closing for some reason under certain throttle conditions.
> 
> I could be completely wrong, but thats what I was thinking.


Could be. It does seem like it totally shuts down and then jumps ahead.


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## LulzT1 (Aug 24, 2015)

justin13703 said:


> Barefeet said:
> 
> 
> > Update. After a week in the shop, Chevy engineers recommended replacing the "catalytic converter-GM (12659575). This was covered under warranty, the bill would have been $1743. The car did a regen yesterday and there was no change, it still runs rough and the CEL cane back on code 2354. I will take it back again.9
> ...


Could be a number of factors. However, IMO it has to be tune related. On the factory tune, my car only bucked lightly during a regen in traffic. After the latest recall in May, it's almost unbearable and any low speed and is noticeable even up to around 50-55mph! The only thing to change was the tune. Other than that headache the car still runs great.


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## Barefeet (Jan 1, 2014)

It could be related to the tune. I'm not sure if my service department has much choice there, Chevy has recommended the last two tunes.


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## sparkola (Jun 9, 2014)

I watch the scan tool while it's regening and engine jumps back and forth between manifold vacuum and boost but only at a specific throttle setting and load which just happens to be any flat road at around 40 mph or less.


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## VtTD (Nov 5, 2013)

Well, I'll share this here since it's related. The buckling has gotten worse on mine recently. Also I've been having Nox #2 CELs that seem to only kick in during regens (the CEL usually clears itself at some point between regens). I complained to the dealer about the buckling and the CEL. The dealer told me NOX #2 needs to be replaced. They had to order it so they gave me back the car and didn't mention anything about the buckling. I called them back after I picked up the car and asked them what they found as far as the buckling goes since I care more about that than a CEL that comes and goes. I have them on a voicemail saying the NOX sensor will fix the buckling. I can't find anything online that says the NOX sensor on any diesel car can cause that, but I'll be happy if they're right! Who knows with this car. If they're not right about, I'm not going to be happy having paid for a sensor that I could get by without fixing for now. I'll repost what happens after the first regen once they fix the sensor.


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## Barefeet (Jan 1, 2014)

Good luck. Mine is still the same. I will take it back after or during the next regen. I would like to have the mechanic drive it during the regen. The part they replaced "catalytic converter-GM" (12659575) actually appears to be the particulate filter. I am thinking the problem may be the software.


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## VtTD (Nov 5, 2013)

Thanks. Good to know about the DPF if that ever comes up. Btw, they should be able to initiate a regular regen and then do the test drive, I believe. This would be different than the service regen, where they just let it sit and burn stuff off.


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## BDCCruze (Jul 12, 2017)

What method do you guys use to know the car is running a regen?


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## Rivergoer (Mar 30, 2017)

BDCCruze said:


> What method do you guys use to know the car is running a regen?


Use an OBDII scan tool. The ScanGauge II is a great product.

http://www.cruzetalk.com/forum/64-gen1-diesel-general-discussion/132666-scangauge-ii-23.html


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## VtTD (Nov 5, 2013)

I can tell just because of the buckling. Linked that to the regen pretty quick because if it's doing that and the engine is then turned off, the fan stays on like it does when you interrupt a regen. And smells like "heat" from outside.


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## Barefeet (Jan 1, 2014)

I use Scangage II


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## sparkola (Jun 9, 2014)

I use a Bluetooth scan tool running an app called Torque and Snipseys diesel plug ins it works great and you can even perform your own service regens with it.


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## Aussie (Sep 16, 2012)

This may not be relevant, but in the Holden Cruze diesel we have a light that comes on when you have to keep driving to complete a rejen. The manual says to keep the engine above 2,000 rpm. My point being maybe if you hold a lower gear to keep the engine revs above 2,000rpm while it is in rejen it might run smoother.


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## Barefeet (Jan 1, 2014)

Aussie said:


> This may not be relevant, but in the Holden Cruze diesel we have a light that comes on when you have to keep driving to complete a rejen. The manual says to keep the engine above 2,000 rpm. My point being maybe if you hold a lower gear to keep the engine revs above 2,000rpm while it is in rejen it might run smoother.


Yes this helps. I use manual shifting to keep RPMs 2k to 3k, however, it still throws a CEL.


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## BDCCruze (Jul 12, 2017)

Aussie said:


> This may not be relevant, but in the Holden Cruze diesel we have a light that comes on when you have to keep driving to complete a rejen. The manual says to keep the engine above 2,000 rpm. My point being maybe if you hold a lower gear to keep the engine revs above 2,000rpm while it is in rejen it might run smoother.


I believe even the US version has that. It should only come on when the vehicle is running a regen while at low speed so you don't stop. If you frequent express ways you should never see it, at least I have not since I bought mine 30,000 miles ago.

P.S. I won't tell John Cadogan you bought one.


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## Aussie (Sep 16, 2012)

BDCCruze said:


> I believe even the US version has that. It should only come on when the vehicle is running a regen while at low speed so you don't stop. If you frequent express ways you should never see it, at least I have not since I bought mine 30,000 miles ago.
> 
> P.S. I won't tell John Cadogan you bought one.


I already put a reply on his video telling him what I think of his engineering skills. He is one of the most negative guys I have heard, unless you own a Mazda or Hyundai..


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## BDCCruze (Jul 12, 2017)

Aussie said:


> I already put a reply on his video telling him what I think of his engineering skills. He is one of the most negative guys I have heard, unless you own a Mazda or Hyundai..


I can see that. But with how poor sounding he makes Ozzie consumer protections for the auto market, you can't fault him for being customer service focused. 

How has your experience with Holden dealers been?


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## Aussie (Sep 16, 2012)

BDCCruze said:


> I can see that. But with how poor sounding he makes Ozzie consumer protections for the auto market, you can't fault him for being customer service focused.
> 
> How has your experience with Holden dealers been?


It has been good, but since warranty ran out I get my services for half the cost. Mind it helps that nothing has gone wrong so far. Car is 5 years old and battery was replaced at 4 years 8 months, which is reasonable.


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## grs1961 (Oct 23, 2012)

BDCCruze said:


> P.S. I won't tell John Cadogan you bought one.


Cadogan is the sort who will contact a vehicle dealer/manufacturer/importer and say, "Give me a car for 12 months or I'll do a bad review of one."

The people who know about this stuff in the auto biz in Oz ignore him, and rumour has it that some of the luxury brands have intervention orders on him so that he cannot approach or contact *any* of their staff.


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## Barefeet (Jan 1, 2014)

I got it back from the service dept. They said to run it for awhile without the Scangage ll and see if there is a difference. I told them I had tried that, however, they had made some changes and wanted me to try it again. I took the gage off and left it home so I wouldn't be tempted to cheat. The first regen the car was bucking like you were turning the key on and off every second. A few times the engine coughed and I thought, this can't be good for the transmission and drive train. The second time it did a regen was after a 700 mile trip, I took it out on the expressway and it didn't seem too bad, however, the CEL came on again. It goes back to the shop next week, I have no idea what they will do. I would like them to check the throttle plate and EGR valve.


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## VtTD (Nov 5, 2013)

Please keep us posted. I'm going back and forth with my dealer now on this whole issue.


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## Barefeet (Jan 1, 2014)

PROBLEM SOLVED!! After several trips to the dealer and a new DPF (covered by warranty) The problem turned out to be lots of carbon in the throttle body and I suspect also the EGR and MAS. The car runs like new while regenerating. Thanks to others on this forum who made me aware of this problem I told the mechanic to check the throttle body etc. They said it was a mess. Now I have to remember how to do this myself as the next time it will be past warranty. I am not sure how much will be covered this time as I have 77k miles, and I have the GM extended warranty plan. I am thinking we should have a sticky topic devoted to cleaning out the carbon on these cars as a matter of maintenance. I am sure that most cars without a delete will have lots of carbon by 70k. Thanks for the help.


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## DslGate (Jun 29, 2016)

Barefeet said:


> PROBLEM SOLVED!! After several trips to the dealer and a new DPF (covered by warranty) The problem turned out to be lots of carbon in the throttle body and I suspect also the EGR and MAS. The car runs like new while regenerating. Thanks to others on this forum who made me aware of this problem I told the mechanic to check the throttle body etc. They said it was a mess. Now I have to remember how to do this myself as the next time it will be past warranty. I am not sure how much will be covered this time as I have 77k miles, and I have the GM extended warranty plan. I am thinking we should have a sticky topic devoted to cleaning out the carbon on these cars as a matter of maintenance. I am sure that most cars without a delete will have lots of carbon by 70k. Thanks for the help.


My BIL just bought 14 CTD last month , had same issue as you. Rough running, particularly during regen. Dealer hooked up car, called GM in Detrpit and voila, they said dirty throttle body. Once cleaned, ran like new car. Problem solved: dirty throttle body. Anyone have photo of where it's located on LUZ engine?? Can't be that hard to diy it??


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## Rivergoer (Mar 30, 2017)

This recent thread is pretty helpful with EGR and Throttle Body

http://www.cruzetalk.com/forum/64-g.../210810-my-egr-throttle-plate-experience.html


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## Putterman (Dec 31, 2019)

Barefeet said:


> This started after the recall last December to replace nox sensor and flash ecm. During regens the car bucks and runs rough, it will usually throw a CEL (2453 pressure sensor) I cleared the codes myself a few times and tolerated the rough running. In June I took it in for the CEL 2453 and they re-flashed the ECM. The next time it came on they changed the pressure sensor, but that did not help. I took it back and told them I was tired of this and to fix it. They gave me a courtesy vehicle (brand new Malibu) to drive. Three days later they said the plenum to the turbo was leaking so they replaced it. Today during the regen the car still is bucking and running rough, no CEL yet but I expect it will come on soon. I told them about the broken exhaust bolt that had caused a previous problem. They said they checked for leaks in the exhaust. The car has 74k miles on it so the warranty will not cover this. I am taking it back this Tuesday and they will throw more parts at it I am afraid how much this will cost. Any suggestions what to look for?


Mine bucks noticeably during a regen , I have had the car for 2 years and it's been doing this for over a year now , have 155500 k on it now . Just performed a cleaning of egr valve because of a no start condition. Valve was seized in open position . Runs better than before and starts better as well . Hoping it improves performance during regen . I found that if I manually shifted down to bring rpm above 2000 in pretty much eliminated the bucking during regen. It's worth a try


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## Rick T (Sep 23, 2020)

Barefeet said:


> This started after the recall last December to replace nox sensor and flash ecm. During regens the car bucks and runs rough, it will usually throw a CEL (2453 pressure sensor) I cleared the codes myself a few times and tolerated the rough running. In June I took it in for the CEL 2453 and they re-flashed the ECM. The next time it came on they changed the pressure sensor, but that did not help. I took it back and told them I was tired of this and to fix it. They gave me a courtesy vehicle (brand new Malibu) to drive. Three days later they said the plenum to the turbo was leaking so they replaced it. Today during the regen the car still is bucking and running rough, no CEL yet but I expect it will come on soon. I told them about the broken exhaust bolt that had caused a previous problem. They said they checked for leaks in the exhaust. The car has 74k miles on it so the warranty will not cover this. I am taking it back this Tuesday and they will throw more parts at it I am afraid how much this will cost. Any suggestions what to look for?


I have 2014 Cruze Diesel. It has always bucked during exhaust clean cycle. My fix is to go Manual Transmission. Down gear and keep it above 2000 RPM until cycle is complete. (12-15 miles) I believe this also provides better exhaust clean performance.


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