# Seeking Observations: Regen ID method



## revjpeterson (Oct 2, 2013)

I believe I may have found a easy, almost fool-proof method of identifying when a regen is occurring on the CTD. I could probably keep observing this and come to a firm conclusion, but with regens only occurring every 500-800 miles, it might take me several weeks to come to a conclusive answer. So, I figured if several of us are observing this, we might find that conclusive answer more quickly, as well as eliminate variables like environmental conditions, personal habits, etc. 

I have noticed during the past 2 regen cycles that occurred that this screen may be the key to an easy method for identifying a regen: (the pic is vertical on my computer, but CT wants to make it horizontal and I can't find a way to correct it.) 









Step 1: Navigate DIC to the above screen
Step 2: On flat ground, lift off the accelerator at speed and allow the vehicle to coast for at least 5 seconds. 

When I am in a non-regen state, I have observed that this screen on the DIC will display "99mpg" and the graph will be filled all the way to the top. 

During a regen, I have observed that it also displays "99mpg", but the graph always stays one bar short of full. 

I know we have been using a variety of methods that fairly reliably allow us to identify a regen, but some of them are a bit complicated and are really only accessible to those of us really familiar with the vehicle. If my observation holds true, this would be a very user-friendly way to identify a regen that could be easily accomplished by new CTD owners who might not have as much background with diesel, the Cruze, or automotive knowledge in general. Use the attached poll to report your results. Thanks!


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## Aussie (Sep 16, 2012)

I know when the car is in regen when after switching off the engine the fan roars for a while. If I am driving while the regen is happening and it finishes before my trip does, then all is normal when I switch off.


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## Cruze2.0TD (Feb 12, 2014)

On mine I haven't noticed the bar yet because I rarely have it on that screen, but as mine reads in Litres/100km's being a Canadian car, it will show as a bit more than 0 L/100km's if it is doing a regen, it won't drop below like 0.3L/100 km. Which makes sense, because it has to inject diesel into the exhaust to complete the regen. So I am guessing if I looked at the Economy screen it would be one bar from the top during a regen.


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## plasticplant (Mar 26, 2013)

I actually tried this out and I happened to go into a regen on my trip to WI. What you said is true. Full eco bars in a coast when not in regen. One eco bar short while coasting when a regen is taking place. I will use this "trick" now until we get a light(fingers crossed).


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## MilTownSHO (Oct 9, 2013)

plasticplant said:


> I will use this "trick" now until we get a light(fingers crossed).


We aren't getting a light. GM is not going to take the time/money to add this feature if it was not already included.

Personally the only way I have ever noticed it was in a regen was the screaming fan when I shut the car off.


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## boraz (Aug 29, 2013)

take the picture in landscape


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## revjpeterson (Oct 2, 2013)

3-0 that this is working at this point - so far so good. 

I think most of us are aware of the fan-after-shutdown behavior that goes with incomplete re-gens, but I've also heard reports of this occurring on the gas models, meaning there may be conditions other than re-gens that can cause this behavior. It also can't be observed while driving. 

For us in the U.S. switching to Metric has also been mentioned before, but involves a lot of input on the stick to arrive there and then switch back and may be complicated for those new to the vehicle. 

Watching fuel economy over the course of several miles is also a reliable indicator, but it doesn't provide an instant result. Also, something like a strong headwind could be wrongly interpreted as a re-gen. I know that I have seen 20 mile graphs into a headwind that looked identical to what I would see during a re-gen. 

That's why I found this discovery so intriguing. It's simple, reliable, and instant, which are 3 characteristics that none of the other methods have score a 3/3 on. 

While knowing when their car is or is not in a re-gen state might not seem all that helpful to some drivers, to me it seems like very useful information. For example, if I know I am mid re-gen, and not on a schedule, I can take a little longer drive to let it finish up. Or if I'm driving on a rural highway, and notice a re-gen, then need to slow down to go through a town, I can switch over to manual mode and keep the RPMs up so as not to prolong the re-gen. If I know I am getting close to home or my drive isn't long, I can also use manual mode to drive at highway speed in a lower gear to make sure the re-gen completes, and avoid the need for the re-gen to re-initiate on the next drive. 

I think there are two primary benefits to this:

1. Finishing a re-gen in one drive rather than re-initiating it on the next drive to complete saves fuel because it isn't necessary to raise the exhaust temperature a second time and therefore spend a longer time in a re-gen state than would have been spent completing it the first time. 

2. It also should serve to prolong the life of the emissions system. Since repeatedly heating and cooling objects causes wear, it follows that the more cycles from the regular exhaust temperature to the re-gen temperature and back would equate to faster wear. If the car can finish most of its re-gens in a single cycle rather than an average of, let's say 1.5 cycles, it should result in 50% longer life of the emissions system, particularly the DPF, because it will heat cycle fewer times. Of course this could turn out to be irrelevant if the DPF proves itself to have an average useful life of 300,000 miles. However, since that data is not available yet, being aware of and completing re-gen cycles on the first attempt could prove to be a cost and trouble saving measure if we would find it to be common that a DPF fails at 100,000 or 125,000 miles. 

Thanks for your observations, and I hope others will keep them coming as their cars go through re-gen cycles in the coming weeks.


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## Aussie (Sep 16, 2012)

In my owners manual it claims the DPF will last the life of the car.


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## oilburner (Jun 13, 2013)

for all of us Canadians any time your fuel consumption does not go too 0.0 per litre on full
desel foot off throttle its doing a regen.


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## raffmanlt (Oct 4, 2014)

I am with a lot of other people, I wish there was a way of knowing when it regens if for no other reason I would know when I am doing a mpg test that it will no longer be a good test or if it does it a lot there might be some kind of issue. There are times my mpg drops below normal and I assume it must be in a regen.

However on the fan running like some have mentioned I don't think you can go by that cause I have had several non turbo cars on a hot day or after spirited driving leave the fan on for a while after I killed the engine and took the key out. My turbo cars did that sometimes and I thought it might be to cool the turbo so it doesn't cook the oil. I know they sell aftermarket turbo fan timers you can install on a custom setup made for that reason. I did not install on mine I just made sure I drove easy the last 15 minutes before I shut it down so there would not be any extreme turbo temps which increase after shutdown and no air flow.


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## grs1961 (Oct 23, 2012)

I agree that watching/listening for the fan running hard is not a good indication that a regeneration is in progress - the fan runs fast because the engine is running hot, it could just be that you gave the car heaps before you stopped and it's just hot.


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## diesel (Jun 8, 2013)

Very interesting and observative post. Just to throw this out there in the mix, but I would notice on the 25 mile average screen, my MPG would be 99, but the average would go down while I was coasting. I think this might be directly related to what you observed.


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## revjpeterson (Oct 2, 2013)

diesel said:


> Very interesting and observative post. Just to throw this out there in the mix, but I would notice on the 25 mile average screen, my MPG would be 99, but the average would go down while I was coasting. I think this might be directly related to what you observed.


I noticed that same phenomenon on occasion, but I couldn't find a consistent pattern to it, so it didn't really come to mind when I was working on this. However, it is yet another behavior that can contribute to indicating that a re-gen is in progress.


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## TX CTD (Oct 24, 2014)

I think I would rather know in advance that it is about to happen. I have no experience with it since it's the wife's ride, but I did get the call this week about it telling her to keep driving. Her problem is there's a 20 mile drive to work, but then she may drive 6 or 7 2 block trips during the day before she makes the trip home. Apparently it started trying during the short trips and couldn't finish. She lucked out and had a 15 mile errand she needed to run so she did that one before she did anymore short ones. If she knew in advance that it was getting close then she could plan her day to take care of it, but if she had already made the long errand then she probably would have been walking the rest of the day.


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## Aussie (Sep 16, 2012)

It sounds like the message is doing the same thing the light does. It comes on when a regen needs help and you need to get it done as soon as possible otherwise power is reduced. Even then you should be able to drive keeping the engine above 2,000rpm until it goes away, but you really can't avoid doing this for any length of time. According to my manual the light comes on solid and if you don't take action it will start flashing before finally pulling power right back.


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## 567Chief (Feb 25, 2013)

I have learned that my Cruze will regen about every 450-500 miles based on my driving. I spend most of my time on the highway and when I see my ave MPG drop I switch to the screen with the graph. I notice an obvious drop in the graph for about 15 miles of driving at 60 mph.


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## TDCruze (Sep 26, 2014)

oilburner said:


> for all of us Canadians any time your fuel consumption does not go too 0.0 per litre on full
> desel foot off throttle its doing a regen.


I will have to watch for this, I haven't really noticed any regens so far.


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## Aussie (Sep 16, 2012)

TDCruze said:


> I will have to watch for this, I haven't really noticed any regens so far.


Under normal driving this is a good sign, I have stopped even thinking about it as it is so subtle as to be of no concern unless you get some sort of warning.
As for fuel consumption, isn't this part of it?


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## diesel (Jun 8, 2013)

So I just officially voted "yes". I observed this yesterday on a trip. I see one or two bars below the 99 during the regen and then back up to the top after it's over. It lasted for a few miles this way.


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## Justgot2hunt (Oct 24, 2014)

Very helpful thread ! I have had problems twice (Aug and this month) with the "diesel particulat filter full, continue driving" message but before I could do anything (literally a minute-ish later) I got the 2nd message & engine power reduced/engine light on. I will watch for this also as most of my driving is rural road and highway to work & back (48+ miles each way). Thanks !!


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## diesel (Jun 8, 2013)

Justgot2hunt said:


> Very helpful thread ! I have had problems twice (Aug and this month) with the "diesel particulat filter full, continue driving" message but before I could do anything (literally a minute-ish later) I got the 2nd message & engine power reduced/engine light on. I will watch for this also as most of my driving is rural road and highway to work & back (48+ miles each way). Thanks !!


You should not have this problem with that type of driving. Have you had it in to the dealer?


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## warloc (Dec 10, 2013)

I also have never experienced a regen in 30K miles, if it happened I didn't realize it. I drive 45 miles one way every day doing an average speed of 75 MPH and I make sure to get the turbo going every drive. Maybe trying to squeeze every MPG has something to do with regens and PM filter clogs? Now that I think about it I had some early problems and that's when I was trying to be real easy on the accelerator pedal to see my mileage go up. Not anymore, pedal down and still averaging 38 MPG overall. I climb 5K feet everyday so my MPG is always a little low no matter what I drive, 50 going down, 30 going up.


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## revjpeterson (Oct 2, 2013)

Good (but not all that exciting) explanation of DPF regeneration cycles based on a GM Duramax DPF system. Our system uses the same differential pressure sensors, but injects diesel into the cylinder on the exhaust stroke rather than using the dedicated injector in the exhaust system. 

https://www.youtube.com/watch?v=fNO-oUHmKXU

GM has done a really good job hiding the regeneration cycles on our Cruze, but they are doing them.


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## MilTownSHO (Oct 9, 2013)

warloc said:


> I also have never experienced a regen in 30K miles, if it happened I didn't realize it.


Yes, you have. Like you stated, you just have not noticed it.


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## diesel (Jun 8, 2013)

warloc said:


> I also have never experienced a regen in 30K miles, if it happened I didn't realize it. I drive 45 miles one way every day doing an average speed of 75 MPH and I make sure to get the turbo going every drive. Maybe trying to squeeze every MPG has something to do with regens and PM filter clogs? Now that I think about it I had some early problems and that's when I was trying to be real easy on the accelerator pedal to see my mileage go up. Not anymore, pedal down and still averaging 38 MPG overall. I climb 5K feet everyday so my MPG is always a little low no matter what I drive, 50 going down, 30 going up.


You bring up an interesting point. I wonder how many of the people on here who have had exhaust system problems drive easy. I redline and WOT mine at least once every day.


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## TDCruze (Sep 26, 2014)

So tonight when I got home from work and shut down the Cruze, I noticed that the cooling fan was whirring away and I could smell the heat off of the exhaust. I can only assume that there was a regen cycle in progress. I wasn't paying very close attention prior to getting home, but I did notice that the fuel economy had dropped off. Tomorrow on the way to work I would expect that the regen will try to go again. I will try to keep a close eye on what is happening so I can hopefully identify future cycles. 

It really got me thinking that it would be nice to have a light or some indication that a regen is in progress. I would rather drive for five or ten more minutes and finish the cycle, than shut the car off mid way and blazing hot.


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## plasticplant (Mar 26, 2013)

If the light is already on the dash and just not programmed to light during a regen, I don't see why GM can't update the software with a patch to make the light functional. Heck, if it's a money issue (which I'm sure it is), I'd be willing to pay for the update. It seems like a no brainer. I think everyone would like to know for sure when a regen is taking place. Who knows, it might even cut down on some of the emissions sensor codes that some have been seeing.


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## TDCruze (Sep 26, 2014)

I did note that this morning the regen cycle picked right up after the car warmed up and ran for about 5 mins on the highway. The last eco bar did not fill in when I let off the throttle. Also the mileage was only around 30mpg when it is usually closer to 40mpg. 

The length of time it was in an apparent regen cycle seemed shorter than described by some, it makes me wonder if it didn't have to run a full cycle because it had already started one the previous day?


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## revjpeterson (Oct 2, 2013)

TDCruze said:


> I did note that this morning the regen cycle picked right up after the car warmed up and ran for about 5 mins on the highway. The last eco bar did not fill in when I let off the throttle. Also the mileage was only around 30mpg when it is usually closer to 40mpg.
> 
> The length of time it was in an apparent regen cycle seemed shorter than described by some, it makes me wonder if it didn't have to run a full cycle because it had already started one the previous day?


A shorter cycle on the second try sounds appropriate. The re-gen length is determined by the same differential pressure sensors that signal that the re-gen is needed. I think 22 or 23 grams of soot will trigger the re-gen to begin, and when it gets down to a certain threshold, (I seem to remember that it was 5-7 grams, but not sure) it ends the regen. So if you burned off half of the soot yesterday, then you would have only needed to burn off half today, resulting in a shorter re-gen.


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## revjpeterson (Oct 2, 2013)

There are a couple of footnotes I have noticed on this method so far in 2 re-gen cycles since I first posted:

1. The vehicle must be up to operating temperature. If the motor/trans are cold you won't always reach the top eco bar, even outside of a re-gen. 

2. The vehicle must be traveling above 35 mph (i.e. in 5th or 6th gear) for this to be reliable. At lower speeds/gears, it sometimes works - sometimes doesn't. 

3. Inclines and 15mph+ headwinds may prevent the car from reaching the top eco bar, even outside of a re-gen. I am also wondering if declines or 15mph+ tailwinds could cover up a regen by allowing the car to reach the top eco bar, even during a re-gen, but haven't confirmed that. 

Regardless, it seems that under normal conditions, (warm vehicle, flat road, calm weather, etc.) this indicator is reliable. The 5-1 score confirming the pattern seems to indicate, and I am wondering if the 1 "no" vote is due to one of the above conditions. So, thanks for the input and keep up the good work reporting your observations!


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## Aussie (Sep 16, 2012)

revjpeterson said:


> There are a couple of footnotes I have noticed on this method so far in 2 re-gen cycles since I first posted:
> 
> 1. The vehicle must be up to operating temperature. If the motor/trans are cold you won't always reach the top eco bar, even outside of a re-gen.
> 
> 2. The vehicle must be traveling above 35 mph (i.e. in 5th or 6th gear) for this to be reliable. At lower speeds/gears, it sometimes works - sometimes doesn't.


In my owners manual it says that when the light comes on to try to keep the engine above 2000rpm until the light goes out.


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## Sperry (Aug 3, 2013)

My last regen was 700 miles ago.. I will keep track of the next 2 or 3 regens and see how many miles are driven between them.. I think it's every other tank , about 1300 -1500 miles


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