# CEL and OBD2 codes that appeared today



## Barry Allen (Apr 18, 2018)

CEL came on today with the following codes:

P0403: EGR flow malfunction
P0406: EGR flow sensor A high input
P24A5: (definition unfound), Google search reveals this to be EGR cooler bypass bank 1 control stuck

Any expert opinions of what is happening here?


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## TDCruze (Sep 26, 2014)

Barry Allen said:


> CEL came on today with the following codes:
> 
> P0403: EGR flow malfunction
> P0406: EGR flow sensor A high input
> ...


Could this be directly or indirectly related to your unplugging of the EGR Valve you discussed in another thread? 
Did you ever delete the codes after you plugged it back in?


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## Barry Allen (Apr 18, 2018)

TDCruze said:


> Could this be directly or indirectly related to your unplugging of the EGR Valve you discussed in another thread?
> Did you ever delete the codes after you plugged it back in?


I have no idea. When I unplugged the EGR it was a few weeks ago and I immediately plugged it back in when I saw it was going to be a "hard" code that would eventually limit the speed of the vehicle. After enough restarts the CEL went away on its own.

Yesterday was the CEL showing up for nothing that I actively did, and those are the codes I pulled and then reset.


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## TDCruze (Sep 26, 2014)

Was the engine turned off when you unplugged the EGR?
Did the codes come back since clearing them the other day?


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## Ma v e n (Oct 8, 2018)

I'm not sure I caught whether the light has come on again or not?

Did you CLEAR the DTCs last time you scanned it and these are new?

Or did the the CEL just go off and you never scanned it?

DTCs can stay stored long after the light extinguishes. This is normal


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## Barry Allen (Apr 18, 2018)

TDCruze said:


> Was the engine turned off when you unplugged the EGR?


Yes. I unplugged the EGR on a cold engine and immediately when starting it threw a CEL and a warning message about "service emissions system" and gave me the start of a 75 mile countdown until speed limiting. I turned the car off, plugged the EGR back in, and started it again. The CEL stayed on for a few more starts and then went away on its own.



> Did the codes come back since clearing them the other day?


The CEL has not illuminated today. I don't know about codes as I don't have a code reader at home.


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## Barry Allen (Apr 18, 2018)

Ma v e n said:


> Did you CLEAR the DTCs last time you scanned it and these are new?


I never scanned or cleared anything when I did the EGR disconnect experiment. I was just driving home from visiting a winery and the CEL came on. Checking the codes then gave me the three listed above (four, actually; the last two were duplicates).


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## TDCruze (Sep 26, 2014)

Barry Allen said:


> Yes. I unplugged the EGR on a cold engine and immediately when starting it threw a CEL and a warning message about "service emissions system" and gave me the start of a 75 mile countdown until speed limiting. I turned the car off, plugged the EGR back in, and started it again. The CEL stayed on for a few more starts and then went away on its own.
> 
> The CEL has not illuminated today. I don't know about codes as I don't have a code reader at home.


If it's off now I guess let it be since you don't have a scan tool to check or clear codes. 

If it comes back try and get a hold of a tool that can clear the codes. 

If they come back after that it may be a trip to the dealer.


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## Barry Allen (Apr 18, 2018)

TDCruze said:


> If it's off now I guess let it be since you don't have a scan tool to check or clear codes.
> 
> If it comes back try and get a hold of a tool that can clear the codes.


To be clear: When the CEL came on yesterday I did use a scan tool to pull the codes and to clear them. That's how I posted the codes at the top of the thread.


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## TDCruze (Sep 26, 2014)

Barry Allen said:


> To be clear: When the CEL came on yesterday I did use a scan tool to pull the codes and to clear them. That's how I posted the codes at the top of the thread.


I wouldn't worry then unless they come back, then take it to the dealer if still under warranty.


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## rcruze (Mar 22, 2018)

Maybe something came undone? Have you looked at all of the connections yet?


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## plano-doug (Jul 1, 2015)

rcruze said:


> Maybe something came undone?


That's what I'm wondering. When you get that many codes, and they all pertain to the same thing, EGR, then that's the first place to look. Is the connector plugged in? Is there a wire pulled out of it? Is the harness damaged, as might occur if it inadvertently got re-routed near a hot spot?

Doug

.


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## Barry Allen (Apr 18, 2018)

The only thing I unplugged during my experiment was the connector the EGR actuator. After the CEL and speed limiter warning showed on the display, I shut the engine off and plugged the connector back in. It snapped right into place so it's not possible that it came undone due to there being a positive latching mechanism.

My guess is one of the three codes that I pulled only came up recently on the day the CEL illuminated, as a random malfunction. Once I reset the codes all is doing fine so far.


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## Barry Allen (Apr 18, 2018)

CEL came on today on my way home from work. Code P2457 displayed: EGR cooling system performance. Looks like this code shows up when the temperature of EGR through the cooler is higher than expected.

Dealership will have the car tomorrow afternoon to check it over, and I told them about the prior codes from the 4th.


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## Barry Allen (Apr 18, 2018)

Car was at dealership yesterday afternoon. After about two hours the service writer calls me back to say the initial technician looking at it was not aware it was a diesel. The diesel trained technician was swamped with work and couldn't look at it that day. The service manager agreed to reset the codes and give me the car back and we'll see if it holds on without any more errors. I'll be leaving to drive to Seattle next week so I'll have a long distance trip to see what other problems show up.


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## sailurman (Sep 29, 2016)

So you are leaving from Illinois to Seattle and back with a potentially speed limiting DTC? Keep that code reader hooked up LOL and good luck!


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## Barry Allen (Apr 18, 2018)

sailurman said:


> So you are leaving from Illinois to Seattle and back with a potentially speed limiting DTC? Keep that code reader hooked up LOL and good luck!


The speed limiting code only occurred when I physically unplugged the EGR actuator valve as an experiment. It did exactly what I expected. The subsequent CELs have not had speed limiting issues; just a "soft" CEL on the dash that I'm willing to ignore.

And yes, I'm leaving Illinois for Grand Tetons, Yellowstone, Craters Of The Moon, Crater Lake, Mt St Helens, and then Seattle.


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## mkohan (Dec 19, 2015)

Enjoy the trip.


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## TDCruze (Sep 26, 2014)

Barry Allen said:


> The speed limiting code only occurred when I physically unplugged the EGR actuator valve as an experiment. It did exactly what I expected. The subsequent CELs have not had speed limiting issues; just a "soft" CEL on the dash that I'm willing to ignore.
> 
> And yes, I'm leaving Illinois for Grand Tetons, Yellowstone, Craters Of The Moon, Crater Lake, Mt St Helens, and then Seattle.


Nice! 

I am heading to Seattle tomorrow on a road trip as well. 

Hope the drive goes well and without issue.


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## Rivergoer (Mar 30, 2017)

Beautiful country, enjoy.

Keep us posted on how the Cruze does.


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## IndyDiesel (May 24, 2015)

The drive thru the Tetons is one of my favorite drives of all time for me. Enjoy the trip and hope your Cruze does well.


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## Barry Allen (Apr 18, 2018)

Rivergoer said:


> Keep us posted on how the Cruze does.


The drive up through the Tetons was amazing. The car performed well enough but still seems to be lagging at altitude (though probably not as much as any normally aspirated engine does). What is the critical altitude of the compressor?

Today the CEL came on again as I was pulling out from a scenic overlook above the Snake River. I pretty much floored it to get up to speed and it's on again. No garage in the area is open over the holiday weekend so I'll have to just leave it alone and hope it clears up on its own.


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## Rivergoer (Mar 30, 2017)

Glad the trip is going well, it is indeed awesome country up there. 

I regularly drive my diesel through Flagstaff, AZ (elev 7,200) and never notice any performance degradation whatsoever. 

I wonder if that recurring CEL may have something to do with the lagging?


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## Barry Allen (Apr 18, 2018)

Rivergoer said:


> I regularly drive my diesel through Flagstaff, AZ (elev 7,200) and never notice any performance degradation whatsoever.


You can floor the car and 1,500 RPM is where boost starts to build to a noticeable level - below that engine speed and the compressor (turbocharger) is basically useless.

Once I ascended about 5,000 feet ASL was where I noticed boost was lagging just a little bit. Call it about 1,700 RPM when the boost starts to kick in with urgency, so the thin air is affecting things at least a little bit. Getting to locations above 7,000 feet and the power is definitely slackened off a little bit. It's certainly nothing dramatic, but it's noticeable.

Other than that, I can set the cruise control at basically any speed and the car charges up steep grades without having to downshift.


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## Barry Allen (Apr 18, 2018)

Things I have noticed:

1. Out west there are a lot of unattended pay-at-the-pump diesel pumps that offer off-road diesel. In Wyoming I filled up with dyed ULSD by just paying at the pump.
2. In Yellowstone National Park I drove through some areas with natural hot springs that stink from sulphur emissions. It got me thinking: We process diesel fuel to remove sulphur so it doesn't clog the DPF, yet I'm driving through clouds of sulphur dioxide that I can smell. It makes me wonder how much of that sulphur clogged up my DPF by going into the air intake of the engine.
3. OH MY GOD there is absolutely nothing in Southeast Oregon. It's desert without a soul in sight. I turned off onto a side highway and a sign said "NEXT GAS 90 MILES" and then I drove for 1 hour 45 minutes without seeing another car or human.
4. Apparently Oregon doesn't let you pump your own fuel. The pump attendant told me it sounded like my engine had a knock. "Yeah, it's got four knocks. One in each cylinder. Fill it up with diesel." And then I had to stand there at the pump and watch him to make sure he didn't fill the car with unleaded.


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## MRO1791 (Sep 2, 2016)

My 2017 threw that P2457 code yesterday. Light is still on, but it's a historical fault code now. All temperatures appear normal, coolant level is normal. Dealership doesn't think it's urgent to get it in for service. No noticable issues with the engine, however MPG seems to be below it's normal average. 

Sent from my Moto G (4) using Tapatalk


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## TDCruze (Sep 26, 2014)

MRO1791 said:


> My 2017 threw that P2457 code yesterday. Light is still on, but it's a historical fault code now. All temperatures appear normal, coolant level is normal. Dealership doesn't think it's urgent to get it in for service. No noticable issues with the engine, however MPG seems to be below it's normal average.
> 
> Sent from my Moto G (4) using Tapatalk


Could be a bad EGR temp sensor, exhaust temperature sensor, clogged egr cooler or a few others which it sounds like you have already checked.
Lower MPG is a symptom, so could be related. 
By "all" temperatures appear normal, have you checked exhaust sensor temperatures?


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## MRO1791 (Sep 2, 2016)

TDCruze said:


> Could be a bad EGR temp sensor, exhaust temperature sensor, clogged egr cooler or a few others which it sounds like you have already checked.
> Lower MPG is a symptom, so could be related.
> By "all" temperatures appear normal, have you checked exhaust sensor temperatures?


Thanks, I have the Torque App with the Bi-scan for GM and the diesel Cruze. I checked the EGR 1and 2, and all 3 EGTs and all seemed normal on my test drive. The fault code is historical, so maybe the condition that caused it is not currently present. 

Sent from my Moto G (4) using Tapatalk


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## spaycace (Feb 9, 2012)

I’ve recently had P24A5 pop up 3 times: first time on May 12th, cleared the code. Second time June 30th, cleared code again. Number 3 was this morning (July 10th) on the way home from work. Dealership can’t get to it for a week and already saying they want to keep it for a couple days! Are there any TSBs out there that I haven’t been able to find? Also, will the car be good to drive until I get it to the dealership? I commute 120 miles a day for work, so not having my fuel miser is a pain in my @$$. Anyone else have experience with this issue and/or know of possible causes/corrective actions?


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## Ma v e n (Oct 8, 2018)

24A5 is for her cooler bypass being stuck. No TSBs


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## spaycace (Feb 9, 2012)

Got my Cruze back from the dealership (dropped it off on a Thursday morning, picked it up the following Monday around 1:00) and even though they had it over the weekend, determined that the P24A5 I was experiencing was not "active" when they were troubleshooting the problem. I was told the code was stored in the history, but was not actually set at the time they checked it out, event though the CEL remained on for them to check it out. Can't believe they had my car 3.5 workdays, and could only say "Well, it's not an active code, but it is stored in the history. Bring it back if it comes on again." WOW! If it weren't still under warranty, I'd be taking it to a local diesel only shop that was recommended by another mechanic I truly trust. Oh well ... I'm still at 48 mpg Lifetime average, so I guess I can't complain too much yet.


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## BodhiBenz1987 (Jan 13, 2018)

spaycace said:


> Got my Cruze back from the dealership (dropped it off on a Thursday morning, picked it up the following Monday around 1:00) and even though they had it over the weekend, determined that the P24A5 I was experiencing was not "active" when they were troubleshooting the problem. I was told the code was stored in the history, but was not actually set at the time they checked it out, event though the CEL remained on for them to check it out. Can't believe they had my car 3.5 workdays, and could only say "Well, it's not an active code, but it is stored in the history. Bring it back if it comes on again." WOW! If it weren't still under warranty, I'd be taking it to a local diesel only shop that was recommended by another mechanic I truly trust. Oh well ... I'm still at 48 mpg Lifetime average, so I guess I can't complain too much yet.


When did the CEL come on previously ... i.e. was it right after you started the car? As far as I know, the cooler bypass valve only opens to allow air through the bypass when the car is warming up. My guess would be it is sticking shut when the car needs to open it to warm up at first ... because I would think if it stuck open you'd be getting other codes for EGR/intake temps as they would be high if it was always open. It is surprising the dealer would dismiss the issue when it actual set a CEL ... I expect the "no CEL, no problem" struggle but there's obviously an issue if the light has come on repeated times. Hopefully they'll be able to do something if it sets again, but in the meantime I would theorize that it is only something affecting that initial warm-up phase under certain conditions.


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## Snipesy (Dec 7, 2015)

Some codes will never show up as current and GM doesn't really do a good job of explaining why.


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## spaycace (Feb 9, 2012)

The CEL comes on while driving down the road, this time at 60 mph, and the freeze frame data shows a large difference between EGRT 11 (968 deg) and EGRT12 (277 deg) so maybe that has something to do with it. So ... I took the car to dealership again while the CEL was still on after it appeared on my drive home from work, so they could see it without my ever having shut the car off, (and didn't check the codes myself until after the dealer was done but they didn't reset the CEL). After 2 days in the shop again, they came back with needing to replace the EGR valve (not the cooler bypass valve as I suspected from post #32 above). Of course, it's on a national back-order, so who knows when it will be repaired. I find it slightly odd that the CEL was coming on roughly every month. I received a notice from Rockauto.com that the genuine GM part was available to order from them, so I would guess that my local dealership should soon be scheduling my part replacement. I may just buy 1 or 2 of them from Rockauto as a backup, as well as a cooler bypass valve if this is going to be an issue ... or perhaps I'll get rid of some of that crap after it's out of warranty, as I literally watched my average mpg drop from 48 to 29 during a regen cycle! I don't want to get rid of this lil diesel, cuz I love driving it, and love the MPG as it's better than my 2018 Volt on my commute to/from work when checking the MPGe after my round trip. That's saying a lot because I only drive the Volt at 75 mph and "hyper mile" the $#!+ out of it, compared to the 80 mph I drive the Cruze. Hoping the eventual EGR valve replacement takes care of the problem.

UPDATE: Here it is a lil over 3 weeks after EGR valve was replaced, and same code reared it’s ugly self again! I’m still not sure why they replaced EGR and not EGR cooler bypass (which is what the dealership’s printout says) to resolve this problem. So ... it’s another trip to the dealership next week, while driving around with the CEL illuminated.


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## CruzeQC (Oct 3, 2020)

Hello spaycace

I myself got the P24A5 code yesterday on my 2018. It's the only code showing at the moment. I was running errands in the city and the car was not at full operating temp (the temp needle in the middle). Outside temp was -3c (26F).

My trust mechanic, not dealer, is taking a look this morning. The dealer in my area is beyond abysmal service (couldn't find a more intense word in English) so I don't want to go there for now.

I couldn't find much information about that code except it's related to EGR Cooler valve stuck. Car goes great otherwise. 90k KM (about 56k miles).

How did it go on your side after your last dealer check up? I'll let you know how it goes on my side.


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## Barry Allen (Apr 18, 2018)

CruzeQC said:


> Hello spaycace
> 
> I myself got the P24A5 code yesterday on my 2018. It's the only code showing at the moment. I was running errands in the city and the car was not at full operating temp (the temp needle in the middle). Outside temp was -3c (26F).
> 
> ...


That code resulted in a warranty recall where Chevy replaced the EGR cooler assembly. There are new parts numbers, but I don't know what changed. It was about a 5-6 month wait because the part was on backorder (Gee, I wonder of others are having the same problem?!) and then the strike last year delayed the part being delivered and delayed getting me an appointment to install it. There were other, more urgent customers waiting (people who did not have a car to drive) so I got broomed to later in the repair schedule when they could catch up on the backlog of stuff waiting.


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