# Reduced power message with engine check light on



## phil1734 (Aug 30, 2019)

Hmm...

Let's see here...

You know what the problem is.
You know why the problem occurred.
You know how to rectify the problem.
And you've actively chosen not to.

But now you're upset the problem persists?


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## Z71 (Jan 1, 2019)

Actually I am asking if continued driving in the power reduced mode will automatically initiate the regeneration cycle. Or, is dealer initiated corrective action the only alternative here? Also, can continued driving in the reduced power mode cause engine damage or other problems?

If I use a regular OBDII code reader, will I get the proper diagnosis for the engine check light and corresponding reduced power mode? I would like to do at least that. At this time I am just guessing what the probable cause is. According to the owner's manual, if you press the start button and hold it for at least 5 seconds, this places the vehicle into a diagnostic mode, so I assume this is the way to check for the codes.


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## Barry Allen (Apr 18, 2018)

I had the same issue. I don't know why the message came up but I took a few days of just driving the car for it to clear up. I was pulling away from a traffic light when I was flooring the accelerator (because that's what it takes when the engine won't rev past about 2,400 RPM) and the engine just "woke up" with full power to where it laid some rubber and activated traction control to dial the power back again.

Take it for a long highway drive. You'll have to hold it flat to the floor for the car to do about 65mph (slower going up hills!) but it will run. Try that to clean the DPF out a bit to where the power restriction goes away.


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## Snipesy (Dec 7, 2015)

An actual Reduced Engine Power message is almost always a High Pressure Fuel issue. Not always. But most of the time.

DPF FULL / Keep driving does not cause a reduced engine power.


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## Barry Allen (Apr 18, 2018)

Snipesy said:


> DPF FULL / Keep driving does not cause a reduced engine power.


It did on my car within a short period after I bought it. The warning flashed that the DPF was full, continuous driving was necessary, and the power was limited to about 2,400rpm even when holding the accelerator to the floor.


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## Snipesy (Dec 7, 2015)

Barry Allen said:


> It did on my car within a short period after I bought it. The warning flashed that the DPF was full, continuous driving was necessary, and the power was limited to about 2,400rpm even when holding the accelerator to the floor.


I should clarify. They are two seperate messages. Important not to mess them up. You can get REP without a dpf issue. You can get the dpf warning without a rep.


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## Z71 (Jan 1, 2019)

Update:

I downloaded the codes with my OBDII reader and got these two codes:

P244A (no description) However, this code stands for "Diesel Particulate Filter Differential Pressure Too Low Bank 1"

P2459 (DPF regeneration frequency)

So my initial guess was correct, the engine light with reduced power mode was thrown most likely due to too many regeneration cycles being interrupted. This was because I used the car only for short trips before and it sat for weeks without being used..

After about two hours I took the car for a short drive and the reduced engine power mode came up again along with a check engine light. This happened after about 5 minutes of driving. I came back home, parked the car for about 4 hours and took it for another drive (this time without clearing the codes). After the car sits with the engine off for a while it always reverts to full engine power. This time the reduced engine power did not come on and I drove the car for about 45 minutes and the message never came back. However, the check engine light remained on. The car drove in full power mode the whole time. Does this mean it went through a regen cycle? I wonder if I clear the check engine light will the reduced power mode come on again? Hopefully not.


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## Snipesy (Dec 7, 2015)

Z71 said:


> Update:
> 
> I downloaded the codes with my OBDII reader and got these two codes:
> 
> ...


I would say the DPF is fine and its the diff. pres. sensor and / or piping. My recommendation would be to have the dealer replace the sensor (its like a 10 minute job). If problem persists, replace pressure pipes (this is like a 3 hour job on the Gen 1, idk about Gen 2).


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## BodhiBenz1987 (Jan 13, 2018)

Looking at the description for those codes I would think the same thing that Snipesy said ... both could be related to inaccurate sensor (or sensor line) readings. The sensor might be giving the ECM values that 

I know I'm hijacking the thread (sorry) but this is the first I've actually heard of the regeneration frequency code and based on the description I'm kind of puzzled as to why my car has never thrown it. This it the description: "The ECM detects that the actual soot level is greater than an expected soot level when regeneration is triggered." I would assume the "actual soot level" is the diff pressure sensor reading, while the "expected soot level" would be the estimate based on other engine data. Looking at the GDS2 data that was last pulled from my car, I have a huge gap between those two numbers ... the time before it was even bigger (97% vs 31%, and it did a regen about five miles later). Maybe @Snipesy or someone else who knows this stuff well could explain ... in the red boxed area, aren't the first two data points literally the same thing (hence the same value), and how the ECM interprets "actual soot level"? And the third one would be what the manual is calling "expected soot level?" Unless I'm reading the manual description backwards and what it's saying for that code is the soot level is reading, say, 200% instead of the "expected" 100% when a regen is triggered. In either case a bad sensor or plugged/constricted/damaged line to the sensor could be to blame for your problem, @Z71 's.


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## Snipesy (Dec 7, 2015)

BodhiBenz1987 said:


> Looking at the description for those codes I would think the same thing that Snipesy said ... both could be related to inaccurate sensor (or sensor line) readings. The sensor might be giving the ECM values that
> 
> I know I'm hijacking the thread (sorry) but this is the first I've actually heard of the regeneration frequency code and based on the description I'm kind of puzzled as to why my car has never thrown it. This it the description: "The ECM detects that the actual soot level is greater than an expected soot level when regeneration is triggered." I would assume the "actual soot level" is the diff pressure sensor reading, while the "expected soot level" would be the estimate based on other engine data. Looking at the GDS2 data that was last pulled from my car, I have a huge gap between those two numbers ... the time before it was even bigger (97% vs 31%, and it did a regen about five miles later). Maybe @Snipesy or someone else who knows this stuff well could explain ... in the red boxed area, aren't the first two data points literally the same thing (hence the same value), and how the ECM interprets "actual soot level"? And the third one would be what the manual is calling "expected soot level?" Unless I'm reading the manual description backwards and what it's saying for that code is the soot level is reading, say, 200% instead of the "expected" 100% when a regen is triggered. In either case a bad sensor or plugged/constricted/damaged line to the sensor could be to blame for your problem, @Z71 's.


I honestly have no idea. 90% of GM's description of things just restate the obvious.

Tables like these https://gsi.ext.gm.com/gmspo/mode6/pdf/2018/18OBDG04 Engine Diagnostics.pdf
( you may have to go through TDS to get that I'm not sure) are directly pulled from the software.

Says for P244A "This diagnostic detects a DPF pressure sensor pipe disconnected or clogged or blocked or a removed Diesel Particulate Filter"

Now the table it shows is just zeroed out so it's likely a table the ECM learns over time using some unknown algorithm.


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## BodhiBenz1987 (Jan 13, 2018)

Snipesy said:


> I honestly have no idea. 90% of GM's description of things just restate the obvious.
> 
> Tables like these https://gsi.ext.gm.com/gmspo/mode6/pdf/2018/18OBDG04 Engine Diagnostics.pdf
> ( you may have to go through TDS to get that I'm not sure) are directly pulled from the software.
> ...


Thanks for the link, that has some details that weren't in the AllDataDIY description (will be helpful to have on file or other DTCs too). Unfortunately I don't understand the P2459 description enough to interpret. But it sounds like it's the ratio between the two numbers on my readout sheet (the 92% being delta pressure plus configurable correction block and the 35% being the engine out soot model). However the threshold is listed as 10, which if I'm reading right is the ratio ... as in the soot model would have to estimate 10% loading when the "actual" reading is 100%? It also lists required additional conditions as "few" miles driven/time passed/fuel used (all three must be met) since last regen, as opposed to "many" ... so I don't know how few/many is defined.

Anyhow, it will be interesting to hear how it is resolved for the OP ... hopefully something simple.


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## Snipesy (Dec 7, 2015)

BodhiBenz1987 said:


> Thanks for the link, that has some details that weren't in the AllDataDIY description (will be helpful to have on file or other DTCs too). Unfortunately I don't understand the P2459 description enough to interpret. But it sounds like it's the ratio between the two numbers on my readout sheet (the 92% being delta pressure plus configurable correction block and the 35% being the engine out soot model). However the threshold is listed as 10, which if I'm reading right is the ratio ... as in the soot model would have to estimate 10% loading when the "actual" reading is 100%? It also lists required additional conditions as "few" miles driven/time passed/fuel used (all three must be met) since last regen, as opposed to "many" ... so I don't know how few/many is defined.
> 
> Anyhow, it will be interesting to hear how it is resolved for the OP ... hopefully something simple.


Sadly there is a discrepancy between the PIDs and other calculated data the MDI or Gretio shows, and what is shown in these tables. They just don’t have the same names. The “internal name” might match a PID, or it may not. GM just doesn’t share the needed documentation.


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## Z71 (Jan 1, 2019)

I cleared the codes this morning with my OBDII scanner, took the car for about 1 hour ride, including high interstate speeds. The car performed normally, check engine light or reduced power message did not appear again. I think now that because of shorts trips and many interrupted regen cycles, the DPF was indeed clogged and the differential pressure sensor performed correctly. I am not sure what the acceptable reading limits for the DPF differential pressure sensor are (based on percentage clogging of the filter). I need to take care of the recall regarding the frequent regeneration messaging, so then the dealer can scan the system and see if it is working correctly.

My original question was that if the DPF was indeed clogged and the car responded by reducing the engine power, would the system still initiate the regeneration cycle in the limp mode, or whether a trip to dealer and forced regen cycle was needed to reset the system. Apparently the car still starts the regen cycle even in the limp mode.
And driving in the limp mode is not fun, the biggest hazard is glacial acceleration, the car feels like it is dragging a 10,000 lb anchor behind it. So if you get caught in this mode, be very careful pulling into moving traffic. It is better to wait until the road is clear before you pull out.


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## Snipesy (Dec 7, 2015)

Z71 said:


> I cleared the codes this morning with my OBDII scanner, took the car for about 1 hour ride, including high interstate speeds. The car performed normally, check engine light or reduced power message did not appear again. I think now that because of shorts trips and many interrupted regen cycles, the DPF was indeed clogged and the differential pressure sensor performed correctly. I am not sure what the acceptable reading limits for the DPF differential pressure sensor are (based on percentage clogging of the filter). I need to take care of the recall regarding the frequent regeneration messaging, so then the dealer can scan the system and see if it is working correctly.


Well the codes don’t reflect that. It’s indicated the differential pressure is lower than it should be. That can only happen if the DPF is destroyed (not gonna happen), or like the code states the pressure pipes are leaking or more likely the sensor itself isn’t working correctly.

If the pressure reading is off the ECM will need to work with whatever data it has and since it’s a fail safe system that means thinking the reading is indicating more soot than is actually present. Hence more, shorter duration, regens.


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## Z71 (Jan 1, 2019)

Is there only one DPF differential pressure sensor? The code P244A refers to "bank1". Thanks for the feedback, I am planning to take the car to the dealer anyway for the recall so I will ask them to check the system.


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## Snipesy (Dec 7, 2015)

Z71 said:


> Is there only one DPF differential pressure sensor? The code P244A refers to "bank1". Thanks for the feedback, I am planning to take the car to the dealer anyway for the recall so I will ask them to check the system.


There is only one sensor.

I have my doubts the dealer will be able to diagnose. These things are too difficult to diagnose so unless there is a CEL or corresponding GM doc they will not replace.


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## Barry Allen (Apr 18, 2018)

Snipesy said:


> I should clarify. They are two seperate messages. Important not to mess them up. You can get REP without a dpf issue. You can get the dpf warning without a rep.


Gotcha.

With mine they arrived at the same time and have never recurred.


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## Z71 (Jan 1, 2019)

Snipesy said:


> There is only one sensor.
> 
> I have my doubts the dealer will be able to diagnose. These things are too difficult to diagnose so unless there is a CEL or corresponding GM doc they will not replace.


I think they should be able to retrieve the codes from the ECM memory even if they were cleared. Will see what they say when I take it in for the recall update.


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## Cruz15 (Mar 17, 2016)

My 2015 had the Differential Pressure sensor changed. It still was flaky when I sold it. Readings were odd some times.


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## Z71 (Jan 1, 2019)

Where exactly on a GEN 2 car is the differential pressure sensor located? From what I was able to find out, this is a low cost part, only about $ 30.


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## BodhiBenz1987 (Jan 13, 2018)

Z71 said:


> Where exactly on a GEN 2 car is the differential pressure sensor located? From what I was able to find out, this is a low cost part, only about $ 30.


Facing the car, it is on the right side near where the charge cooler hose meets the intake, sort of under that. I attached some pictures. The sensor itself is not bad to access but the hoses require some disassembly for access. When I had mine done they did both sensor and hoses, but that was because I found a hole in one hose. If only the sensor is suspect I assume they could replace that more easily. The sensor has the hoses ear-clamped on from the factory rather than with adjustable or spring clamps. Even the sensor/hose combination was only a $70 part but with the hoses the labor is more. The sensor is supposed to be relearned as part of the job. It's hard to get a photo of the pipes as they are obscured by a lot, but they connect to two steel pipes that come out of the DPF and converge side by side to the right of the DPF ... you can sort of see them and if you have small hands can feel them under there.


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## CrimsonRain (Oct 4, 2016)

phil1734 said:


> Hmm...
> 
> Let's see here...
> 
> ...


No need to be that way bro. If you aren't apart of the solution you are part of the problem.


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## pfw_dfw (Sep 13, 2018)

Well, I'm stuck 322 miles from home. No warning whatsoever, and having just driven the 322 miles at 70+MPH, the DPF Filter light pops on with "Reduced Power" when I pull into the parking spot at the hotel. Start it after overnight, and Immediately the Reduced Power Light comes on. Tomorrow is Saturday, I have one hope of a dealer open within 5 miles. If they can't fix it, I'm driving the pig home and will screw it up. Normal operation for me is 75MPH for 110 miles 3x a week. I'm done with FRIGGIN POS Cruze. $8K for a transmission, and now this all within a year.

Anyone in Galveston, Texas who can help will win two jelly beans.. I hate this POS.


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## Z71 (Jan 1, 2019)

BodhiBenz1987 said:


> Facing the car, it is on the right side near where the charge cooler hose meets the intake, sort of under that. I attached some pictures. The sensor itself is not bad to access but the hoses require some disassembly for access. When I had mine done they did both sensor and hoses, but that was because I found a hole in one hose. If only the sensor is suspect I assume they could replace that more easily. The sensor has the hoses ear-clamped on from the factory rather than with adjustable or spring clamps. Even the sensor/hose combination was only a $70 part but with the hoses the labor is more. The sensor is supposed to be relearned as part of the job. It's hard to get a photo of the pipes as they are obscured by a lot, but they connect to two steel pipes that come out of the DPF and converge side by side to the right of the DPF ... you can sort of see them and if you have small hands can feel them under there.


The problem was the sensor. It cost me about $ 28 from the local GM dealer. I replaced it myself. No more engine check light or reduced power for the last 1500 miles.


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## Z71 (Jan 1, 2019)

pfw_dfw said:


> Well, I'm stuck 322 miles from home. No warning whatsoever, and having just driven the 322 miles at 70+MPH, the DPF Filter light pops on with "Reduced Power" when I pull into the parking spot at the hotel. Start it after overnight, and Immediately the Reduced Power Light comes on. Tomorrow is Saturday, I have one hope of a dealer open within 5 miles. If they can't fix it, I'm driving the pig home and will screw it up. Normal operation for me is 75MPH for 110 miles 3x a week. I'm done with FRIGGIN POS Cruze. $8K for a transmission, and now this all within a year.
> 
> Anyone in Galveston, Texas who can help will win two jelly beans.. I hate this POS.


$8k for a transmission? Yours must be an automatic because the price of a manual transaxle on gmpartsdirect.com site is just under $ 2k. Another $ 1k or so for labor, so $ 3 should be it for replacing the manual transmission if a dealer does the work. Of course they would probably also replace the flywheel and the clutch which would add another $ 500. Still nowhere close to $8k.

Possibility of being stuck far from home with the "reduced engine power" problem is not very appealing to me either, so I am seriously contemplating ditching this car while it is still under warranty and has low miles. And what is most annoying is that this car will stubbornly go and stay in the low power mode due to some stupid emission related glitch that would have no adverse effect on the engine performance at all. I never had this happen in my gas engine Impala (188K miles) or gas powered Chevy Sonic (101K miles) and I had a defective pre-cat O2 sensor in my Impala causing the engine to run rich.. The engine check light came on, but nothing else happened and the car drove normally. It is perfectly normal for a car computer to force the engine into reduced power or limp mode if there is coolant overheating issue, loss of oil pressure issue, or a severe misfire in several cylinders that could damage the engine.


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## BodhiBenz1987 (Jan 13, 2018)

Z71 said:


> The problem was the sensor. It cost me about $ 28 from the local GM dealer. I replaced it myself. No more engine check light or reduced power for the last 1500 miles.


Good to hear the problem seems to be solved! Did you just replace the sensor, or the sensor and the pipes? Did you need to do a relearn after? Just curious.


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## Z71 (Jan 1, 2019)

BodhiBenz1987 said:


> Good to hear the problem seems to be solved! Did you just replace the sensor, or the sensor and the pipes? Did you need to do a relearn after? Just curious.


I only replaced the sensor. No need for relearn. Just cleared the code with my OBDII reader and it has been fine for the last 1500 miles or so..


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## BodhiBenz1987 (Jan 13, 2018)

Z71 said:


> I only replaced the sensor. No need for relearn. Just cleared the code with my OBDII reader and it has been fine for the last 1500 miles or so..


Nice ... good to know!


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## conemark (Feb 9, 2020)

Just out of curiosity, after the P244A code, did you elect to replace the sensor on your own or after any attempts at dealer service diagnosis?


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## greg7165 (Jul 27, 2020)

Z71 said:


> My 2018 Cruze sedan 6 speed manual has only 6 k miles on it and today was the first time the reduced engine power message came on. That power reduction was really substantial, as the car would not go over 60 MPH even in 6th gear on open road, and it took a long time to get there. I understand that the reason for this power reduction is probably too many interrupted DPF filter regen cycles as I used the car very little in the last few months and only took short trips in it around town. What I am surprised about is that no warning message appeared before the power was reduced.
> 
> I drove the car home, let the engine cool off then restarted the car and took it for a ride. I had normal power for about 10 minutes, after which the reduced power message came on again.
> 
> ...


i had simular problem had to take to dealer they had to force a regen and placed a sensor it was under warrenty


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