# Hello, my old friend, I haven't seen you in a while!



## JLL (Sep 12, 2017)

Doesn't it show itself every time you start the car? Mine does.


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## Barry Allen (Apr 18, 2018)

JLL said:


> Doesn't it show itself every time you start the car? Mine does.


This one returned to stay on. At least it’s not flashing.


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## Barry Allen (Apr 18, 2018)

P0401: EGR FLOW INSUFFICIENT


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## oregon_rider (Jul 21, 2017)

Just curious - how many miles on your car?

jeff


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## Snipesy (Dec 7, 2015)

Barry Allen said:


> P0401: EGR FLOW INSUFFICIENT


Idk some people would view that as a good thing.


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## Barry Allen (Apr 18, 2018)

Snipesy said:


> Idk some people would view that as a good thing.


Yeah, I'm going to let it ride. 

"You mean to tell me there is LESS soot going into the intake of my car?!"


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## Barry Allen (Apr 18, 2018)

oregon_rider said:


> Just curious - how many miles on your car?


67,xxx so far.


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## Barry Allen (Apr 18, 2018)

I remember the early days of VW TDI engines when you could use VAG-COM software to turn down the EGR flow to where it was minimal. It wouldn't trigger a CEL and the flow was so low that the intakes of the engine would never clog up.


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## Snipesy (Dec 7, 2015)

Barry Allen said:


> I remember the early days of VW TDI engines when you could use VAG-COM software to turn down the EGR flow to where it was minimal. It wouldn't trigger a CEL and the flow was so low that the intakes of the engine would never clog up.


You can do this in Gretio but it only works so as long as the phone is hooked up.

The problem is the ECM doesn’t quite adjust correctly. It’s not really a big deal but EGTs lower significantly and this can cause sound problems warming up. Without the EGR the engine needs to run hotter to accommodate but the stock calibration just doesn’t do that.


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## Barry Allen (Apr 18, 2018)

Snipesy said:


> this can cause sound problems warming up


You mean like sharp Diesel clatter in cold ambient temperatures?

That's not an unexpected side effect. The EGR cooler bypass is there to feed more of that hot exhaust gas into the intake during cold starts. You want hotter intake air so you can get reliable, stable combustion when the fresh air intake temperature is cold. 

It's a similar trick that Mazda uses in their Skyactiv-D engines with 14:1 compression ratios - the variable valve timing keeps the exhaust valve open a bit after the exhaust stroke so the intake stroke sucks some of that hot exhaust gas back into the cylinder to mix with the fresh air intake charge. It raises temperatures to get those cylinders lighting off better when it's cold.

We used to just have 21:1 compression ratios and those engines could crank and fire in almost any temperatures without glow plugs!


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## Barry Allen (Apr 18, 2018)

Anyone have tips for removal, inspection, and cleaning of the EGR valve? It's topside on the engine, right? A fairly easy job to do?


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## Snipesy (Dec 7, 2015)

Barry Allen said:


> You mean like sharp Diesel clatter in cold ambient temperatures?
> 
> That's not an unexpected side effect. The EGR cooler bypass is there to feed more of that hot exhaust gas into the intake during cold starts. You want hotter intake air so you can get reliable, stable combustion when the fresh air intake temperature is cold.
> 
> ...


*some problems
But yeah it could definitely take longer for the start up pings to go away. On these small diesels the EGR is basically the only way we can retain heat. The natural dissipation into the block is just way too slow.


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## oregon_rider (Jul 21, 2017)

Barry Allen said:


> Anyone have tips for removal, inspection, and cleaning of the EGR valve? It's topside on the engine, right? A fairly easy job to do?


 yes. it is topside and easy to change the egr valve. I looked at the instructions on alldatadiy.com a while back - factory service manual info is on-line. The egr cooler on the other hand - that looked like a bit more work.

send me a private message with your e-mail and I can print out the instructions and send them to you.

If you have trouble finding an egr valve - I have a new one in the garage.

jeff


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## phil1734 (Aug 30, 2019)

Lol.

I used to send my girlfriend a snap of mine set to Simon and Garfunkel's The Sounds of Silence ("Hello darkness my old friend ... I've come to talk with you again ...") every time mine turned on.

I think my longest streak without it illuminating was about 12,000 miles/14 months through quarantine.


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## Barry Allen (Apr 18, 2018)

oregon_rider said:


> The egr cooler on the other hand - that looked like a bit more work.


The EGR cooler was replaced under warranty. I don't recall the exact mileage, but it was maybe 25,000 miles or around there. It was some CEL codes that the GM technical HQ said replace it, and it was a new part number that presumably has some changes made to it. A few other people here had that done.


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## Barry Allen (Apr 18, 2018)

Snipesy said:


> On these small diesels the EGR is basically the only way we can retain heat.


I think it's a fine balancing act and the engine flip-flops between EGR cooling depending on needs.

During a cold start, you want some of that hot EGR going into the intake so that combustion can be stable, reliable, and as complete as possible. You want hot air in the cylinders for the best combustion possible and you also want hot exhaust temperatures flowing into the catalysts and DPF to warm them up as fast as possible. In freezing temperatures you want hot exhaust gas to drive the moisture out of the DPF so it doesn't freeze or so the moisture doesn't create a goo/slime with soot in the DPF.

Then, when you're trying to warm the engine up in cold weather, you want EGR going through the cooler so that heat is being shed into the coolant. You want the coolant and overall engine temperature to warm up so that the engine can have lower emissions, lower wear, faster warmup, etc., but you also want some heat going into the passenger compartment for climate control.

Then, when everything is running at temperature you want the EGR to be cooled as much as possible so that you can have it cooler when being fed into the intake for lower combustion temperatures for lower emissions. High levels of NOx are formed with high combustion temperatures so you want a lean intake air mixture to lower combustion temperatures, and you have to cool that EGR gas down to lower intake temperatures as much as possible.

Lastly, I'm not 100% certain but I believe the EGR is entirely bypassed when the DPF is going through a regen cycle. You want the hottest exhaust gas possible to heat that DPF up, so the EGR is closed off to make sure the cylinders get the cleanest intake air possible for high combustion temperatures. Those high temperatures are then spiked a little bit more with some extra fuel injected during exhaust strokes to bring the DPF up to temperatures that burn the soot off. NOx probably spikes during regen, but the EPA gives waivers for temporary engine operating conditions that are rare and limited and don't often happen. DPF regen is where it has to be done and NOx output is allowed to be higher to make that happen.


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## Snipesy (Dec 7, 2015)

Barry Allen said:


> Then, when everything is running at temperature you want the EGR to be cooled as much as possible so that you can have it cooler when being fed into the intake for lower combustion temperatures for lower emissions. High levels of NOx are formed with high combustion temperatures so you want a lean intake air mixture to lower combustion temperatures, and you have to cool that EGR gas down to lower intake temperatures as much as possible.
> 
> Lastly, I'm not 100% certain but I believe the EGR is entirely bypassed when the DPF is going through a regen cycle. You want the hottest exhaust gas possible to heat that DPF up, so the EGR is closed off to make sure the cylinders get the cleanest intake air possible for high combustion temperatures. Those high temperatures are then spiked a little bit more with some extra fuel injected during exhaust strokes to bring the DPF up to temperatures that burn the soot off. NOx probably spikes during regen, but the EPA gives waivers for temporary engine operating conditions that are rare and limited and don't often happen. DPF regen is where it has to be done and NOx output is allowed to be higher to make that happen.


The idea of egr emissions wise is having some inert gas (inertish) for combustion heat to mix into.
Otherwise we get micro pockets where NOx formation is spontaneous. Cooling the gas just makes it more effective as a heat sink. As long as the EGR is lower than like 1000F it’s effective.

While diesels run cooler than gasolines this isn’t really true on a microscopic scale. Diesels are significantly hotter than gasolines in the cyllinder simply due to the pressures involved.

Anyway yes EGR shuts off for most of a Regen. I don’t exactly know why, but I’m guessing it’s to prevent choking on your own fuel. It could also lead to lots of combustion in the intake which probably isn’t a great idea.


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## snowwy66 (Nov 5, 2017)

Probably easier to do a regen with egr closed.


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## Barry Allen (Apr 18, 2018)

Snipesy said:


> Anyway yes EGR shuts off for most of a Regen. I don’t exactly know why


To regenerate the DPF you have to heat it up really hot. You want in-cylinder combustion temperatures to be as high as possible, and to do that you need 100% clean intake air so the EGR doesn't quench the temperatures with inert gases. Then, you are also injecting excess fuel to heat it up even more, and you need as much O2 as possible for that extra combustion. Lastly, you want the soot in the filter heated up as much as possible to combust and flow out the exhaust as CO2, and for that you need extra O2 so the carbon (soot) can combine with that and flow through.

EGR would do nothing but hurt performance of regeneration of the DPF. It's got to be bypassed to make it work.


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## Barry Allen (Apr 18, 2018)

The light magically disappeared yesterday, so it's looking like a transient thing. I'm going to take some down time to clean the EGR valve if I can and see what is going on there.


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## CrushTD (Oct 4, 2020)

I've had a transient CEL as well over the past few weeks. I got P2457: EGR low efficiency. It went off for about an hour, came back on, then went off after I let the car sit for a week while I was away on vacation. I also had the warranty replaced EGR, which was a joy and a half.


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## Snipesy (Dec 7, 2015)

CrushTD said:


> I've had a transient CEL as well over the past few weeks. I got P2457: EGR low efficiency. It went off for about an hour, came back on, then went off after I let the car sit for a week while I was away on vacation. I also had the warranty replaced EGR, which was a joy and a half.


The EGR flow is mostly based off MAF.


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## Barry Allen (Apr 18, 2018)

Snipesy said:


> The EGR flow is mostly based off MAF.


Interesting, but not surprising. I doubt there is a sensor to measure EGR flow, so it's all calculated on how much air is flowing through the MAF sensor. Open up the EGR valve and the ECU expects less through the MAF because of the extra air volume coming from EGR. There has to be some logic to it that checks how much the flow is and then throws a CEL if the expected airflow isn't being achieved.


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## Raythion321 (Jul 22, 2021)

Barry Allen said:


> View attachment 294484


I can tell if it’s gonna be a good day or not just by seeing this little treasure on the dash.


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## Snipesy (Dec 7, 2015)

Raythion321 said:


> I can tell if it’s gonna be a good day or not just by seeing this little treasure on the dash.


Electric tape works well.

And anyone for about $1500 in tools can just disable DTCs themselves








GitHub - Snipesy/Cruze: Unlocking the Cruze, one byte at a time.


Unlocking the Cruze, one byte at a time. Contribute to Snipesy/Cruze development by creating an account on GitHub.




github.com


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## Barry Allen (Apr 18, 2018)

Snipesy said:


> Electric tape works well.


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## Barry Allen (Apr 18, 2018)

IT'S BACK!

P0401: EGR FLOW INSUFFICIENT


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## Barry Allen (Apr 18, 2018)

Just a theoretical question here for those who know: What happens if you install a block-off plate in the EGR?

Does it simply illuminate the CEL and that's all? Or do you get warnings that count down to speed restrictions?


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## Barry Allen (Apr 18, 2018)

It’s back!

P0401: EGR FLOW INSUFFICIENT


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## Barry Allen (Apr 18, 2018)

It's back again today!


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## Snipesy (Dec 7, 2015)

Barry Allen said:


> Just a theoretical question here for those who know: What happens if you install a block-off plate in the EGR?
> 
> Does it simply illuminate the CEL and that's all? Or do you get warnings that count down to speed restrictions?


If you unplug it: A CEL (assuming there is no CURRENT countdown).
If you block it without unplugging: I have no idea.
If you unplug and BLOCK: Same as just unplugging, it.


This is because the EGR Diagnostic takes precedence over the SCR. As such, the SCR diagnostics will never run. And you don't get a countdown.... That's just how GM/Bosch programmed it....

Soooo yeah you can kinda bypass the emissions this way.

For the most part the DPF can function without EGR. It just takes longer to warm up on cold start.


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## Barry Allen (Apr 18, 2018)

Snipesy said:


> If you unplug it: A CEL


When I unplugged it as a test, the dashboard immediately displayed a 175-mile countdown to speed limitations.


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## Barry Allen (Apr 18, 2018)




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## JLL (Sep 12, 2017)

Barry Allen said:


> It’s back!
> 
> P0401: EGR FLOW INSUFFICIENT


🎶 It's the end of the world as we know it.
🎶 It's the end of the world as we know it.
🎶 It's the end of the world as we know it.
🎶 And I feel fine!"


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## Snipesy (Dec 7, 2015)

Barry Allen said:


> View attachment 296355
> 
> 
> View attachment 296356
> ...


Ooops. For some reason I thought this was gen 1 .
Yeah, GM fixed that. Mostly. Just plug it back in and drive. It'll go away.


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## Barry Allen (Apr 18, 2018)

It's back again!


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## Barry Allen (Apr 18, 2018)

The light came back again!

I think I figured it out. I was going somewhere for an appointment and it was raining, and I sat in the car at idle (with the A/C on to keep humidity down) for about 20 minutes. After that, driving away, the light came on.

The prior time was when I was taking my mom on errands and we were stuck in the Wendy's drive-thru for a serious 20 minutes. It was while they were transitioning from breakfast to lunch, and this Wendy's isn't very efficient or well-staffed in the first place. Anyways, after idling, the light came on during the next drive.

It appears that idling has some soot clogging up the EGR valve and it triggers the light the next time I drive the car (when the ECU detect low EGR flow due to the soot clogging it). Any highway driving in the following days must blast it out of there and then the light goes off after a while.


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## Cruz15 (Mar 17, 2016)

Could it be a leaky injector? What would cause that much soot? Just idling causes massive soot? Sounds like the map is messed up?


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## Barry Allen (Apr 18, 2018)

Cruz15 said:


> Could it be a leaky injector? What would cause that much soot? Just idling causes massive soot? Sounds like the map is messed up?


I don't know, but that seems to be the recent pattern. The time prior to these two recent CELs was it coming on when I was doing highway driving, so I assumed it was kinda random. These last two times have been immediately after idling for some period of time (about 20 minutes each time). I left the Wendy's drive-thru, took my mom to her nail appointment, and when we left the CEL came on. I left the place where I was idling in the rain waiting for it to fall off, and when I left after the appointment the CEL came on.

Nothing significant happens when the light is on, so I really don't care about it. I'm not going to fix it right now. If it gets to where I have countdowns to speed restriction, I'll probably invest the money in tuning the car to eliminate the EGR problem. Once tuned I'll find a weekend where my cousin and I can yank the intake manifold to do a complete cleaning and maybe remove the swirl flaps as well, if that's easy to cut them out of there and block off any possible holes.


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## Barry Allen (Apr 18, 2018)

Cruz15 said:


> What would cause that much soot? Just idling causes massive soot?


Comparatively, yes.

Modern Diesel engines have very high pressure injection and a nice injector spray pattern compared to old engines. Old engines had pintle injectors that were like squirt guns, and the fuel spray depended on air tumble in the swirl chambers to mix the fuel. When fuel was pennies a gallon, no one cared if the exhaust was a little dirty with wasted fuel going out the tailpipe because it was so cheap.

Modern Diesel engines can run extremely clean exhaust with clean air in the intake... but then combustion temperatures are so high that NOx production is also high. It's a constant balancing act to get enough EGR in the engine to cool the combustion temperature (because less O2 means lower combustion temperatures) to get less NOx output. The new problem created with this EGR flow is that we are wasting fuel because the lower O2 level in the cylinders leaves some of the fuel unburned - it comes out as soot.

At idle, the engine is typically running very high EGR levels. I've heard it is up to 50% EGR at idle to keep NOx production low, and I believe it has to do with exhaust temperature not being high enough for the NOx catalyst to function efficiently. If the catalyst can't clean up the exhaust the only way to keep NOx low is to not produce it in the first place.

Comparatively speaking, lots of soot is generated at idle because the EGR is choking the engine so much.


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## Goodluckgluck (Nov 13, 2021)

Have you had your EGR cooler replaced or cleaned? Mine required replacement at 42k for being plugged.


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## Barry Allen (Apr 18, 2018)

Goodluckgluck said:


> Have you had your EGR cooler replaced or cleaned? Mine required replacement at 42k for being plugged.


My EGR cooler was replaced at about 15,000 miles (I don't currently remember the exact mileage) because a couple of codes from the CEL being on was a trigger for GM technical at HQ recommending replacing the part. Apparently there was a known issue, there was a replacement part that was updated somehow (different part number), so it was replaced under warranty. It took about 5 months for the part to actually arrive at the dealership because it was made in Europe, was on backorder for a while, and then it was in the middle of the GM strike where parts weren't shipping for a while.


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## Barry Allen (Apr 18, 2018)

It's back again today! It's rainy and incredibly humid, so maybe that's got something to do with it clogging up once in a while? That's twice in a row where wet, rainy weather was around at the time that the light came on.


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## Barry Allen (Apr 18, 2018)

This time there are secondary codes:

P0403: EGR CONTROL CIRCUIT
P0406: EGR POSITION SENSOR CIRCUIT HIGH VOLTAGE

Any thoughts?


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## Cruz15 (Mar 17, 2016)

Apparently you could have a wire that has a short or wiring leading to the EGR. P0406, Trace or replace.
Clean the EGR with WD40 or another solvent and or the intake may be carbon ed up for P0403.
Google says so.


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## Barry Allen (Apr 18, 2018)

Cruz15 said:


> Apparently you could have a wire that has a short or wiring leading to the EGR. P0406, Trace or replace.
> Clean the EGR with WD40 or another solvent and or the intake may be carbon ed up for P0403.
> Google says so.


I noticed these are the same codes that originally led to my EGR cooler being replaced (under warranty) with the updated part number for whatever they changed on that part. Now those codes are back.


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## Goodluckgluck (Nov 13, 2021)

Barry Allen said:


> I noticed these are the same codes that originally led to my EGR cooler being replaced (under warranty) with the updated part number for whatever they changed on that part. Now those codes are back.


Hey mine came back on too! EGR cooler efficiency and cooler bypass valve stuck codes.

Back to the dealer for the 3rd time.


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## Barry Allen (Apr 18, 2018)

It was on Thursday and turned off Saturday. That was quick.


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## Goodluckgluck (Nov 13, 2021)

Mine has also been on and off every few days.


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## Goodluckgluck (Nov 13, 2021)

So this is my car's 3rd time at the dealership. NOW they're saying my ecm needs to be reprogrammed and it's not covered under warranty, after replacing my EGR bypass valve the first time and my EGR cooler the second time under warranty. 


I asked for a TSB or an SSM which would lead them to this conclusion. They said there wasn't one.

I said okay fine but if you're wrong and my light comes back on then that's on you, it sounds like they are throwing darts now.


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## Barry Allen (Apr 18, 2018)

Goodluckgluck said:


> NOW they're saying my ecm needs to be reprogrammed and it's not covered under warranty


I could be entirely wrong, but that sounds like the dumbest explanation I've ever heard.

I know there were at least two ECU updated done on my car. I have some Carfax report that mentions an update done when the car was delivered to the dealership, done for some emissions reason. That could just be a matter of new programming pushed out for already-built cars and it's easy to plug the computer in and do it. Lots of cars get ECU updates for emissions, sometimes spread out over years. Later, there was a recall of what I believe was all 4-cylinder Diesel engines in GM products (the Duramax engines in the Colorado/Canyon pickups and also in the Chevy/GMC vans). It was some update for a fault where the engine could be malfunctioning and the CEL wouldn't illuminate, so it was just another update pushed out and a dealership did it for me in about 10 minutes.

So, what are their exact reasons for saying the ECU needs reprogramming? Those things either break with some major malfunction fault, and that's fairly rare. Or they need a programming update because there is something new that's released.

This sounds like a total horse manure answer from them.


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## Barry Allen (Apr 18, 2018)

Goodluckgluck said:


> it sounds like they are throwing darts now.


Totally. It's the equivalent of them "turning the computer off and turning it back on" to see if that fixes the problem.

Remember that almost every mechanic is like regular people and anything the computer does is voodoo magic to them. It's the same as about 99.999% of other humans. The only exceptions are some old, grey-bearded mainframe computer programmers who actually understand what the magic box is doing. My grandfather was in the navy and did computer programming with vacuum tubes and mechanical relays. My mother did computer programming with punch cards. They had an idea of what a computer program does. Anyone today? It's magic to them - strange, voodoo magic.


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## Goodluckgluck (Nov 13, 2021)

Barry Allen said:


> I could be entirely wrong, but that sounds like the dumbest explanation I've ever heard.
> 
> 
> So, what are their exact reasons for saying the ECU needs reprogramming? Those things either break with some major malfunction fault, and that's fairly rare. Or they need a programming update because there is something new that's released.
> ...


I was trying to pry it out of the service advisor as to what lead them to their conclusion. He just said "the tech said there was a programming from GM that should take care of the problem". I asked if there was any literature like technical bulletins or SSMs that would I could read and he said "no". Typically you wouldn't reprogram the ECM unless explicitly told to do so by GM so I think they are just hoping it sticks. 

I said sure go ahead but if they are wrong (which I'm reasonably certain they are) then I'm not paying for the programming. I'm having them put at least 100 miles on the car, the light should definitely turn back on in that time.


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## Barry Allen (Apr 18, 2018)

Goodluckgluck said:


> they're saying my ecm needs to be reprogrammed and it's not covered under warranty


Unrelated story time:

I owned a Dodge Neon ACR that I had put some go-fast goodies on the car. It had Comp Cams, an exhaust header, and a cold air intake (the stock one was absolute garbage, so this was one that actually worked) and I could say it probably made horsepower approaching 200 (stock was 150). Seat-of-the-pants dyno wants me to say in the 190 range because that car was fast. This was achieved with an aftermarket ECU and it required premium unleaded, which wasn't really a problem.

Anyways, I used to take advantage of the Dodge dealership when they offered $9.95 oil changes. It was a MOPAR filter and up to 5 quarts of MOPAR oil. Conventional oil, but the car wasn't requiring synthetic so I didn't care. I changed the oil every 3,000 miles with that offer and the dealership would give me the left-over 1.25 quarts in the bottles for topping off between changes.

One day I'm there for an oil change and the service manager has to tell me my car won't start after it's been changed. I start asking them to tell me _EXACTLY_ what they did to it. Turns out there was some ECU update pushed out by Dodge for some reason, and the standard process for the oil change guys was to plug the cars into the computer for ECU updates if the dealership system flagged the VIN of the vehicle as needing the update. They bricked the aftermarket ECU in my car.

The car was there for 3 days while they got a replacement aftermarket ECU shipped via UPS and put in the car.

From that point on I would always tape a note to the steering wheel telling any repair technician to NEVER plug the car into the computer for any updates!


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## Barry Allen (Apr 18, 2018)

Goodluckgluck said:


> "the tech said there was a programming from GM that should take care of the problem"


I should ask about it for my vehicle. It's entirely possible there is a tweaked/updated firmware that GM won't bother issuing a TSB, and it's just something that's in their computer system for techs to "Do this if you get around to it while the car is in for service."


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## Barry Allen (Apr 18, 2018)

Goodluckgluck said:


> He just said "the tech said there was a programming from GM that should take care of the problem".


If you get the chance to ask them, try to find out what the date of the ECU update is. Like, if their computer shows a date it was released to the fleet. I'd like to compare that date to the last update I was given under warranty and if it's obviously a newer ECU update I'd consider getting it done to my car.

I don't know if there is any way to check a software version without plugging it in to the computer, so that's not something I can do to compare version numbers. The date of release might be the best estimate to tell if there is actually something new out there for our cars.


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## Goodluckgluck (Nov 13, 2021)

Barry Allen said:


> I should ask about it for my vehicle. It's entirely possible there is a tweaked/updated firmware that GM won't bother issuing a TSB, and it's just something that's in their computer system for techs to "Do this if you get around to it while the car is in for service."



I'm trying to give them the benefit of the doubt, I just have a nagging feeling I'll be back for a fourth time though. 

I'll ask if they know anything about the particular update. I'm guessing it's probably too late to ask what the current calibration was, I think they've all ready reprogrammed it at this point.


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## Barry Allen (Apr 18, 2018)

Goodluckgluck said:


> I'll ask if they know anything about the particular update. I'm guessing it's probably too late to ask what the current calibration was, I think they've all ready reprogrammed it at this point.


Do you have any update? They should be able to tell you when the latest, current calibration was released.


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## Goodluckgluck (Nov 13, 2021)

Barry Allen said:


> Do you have any update? They should be able to tell you when the latest, current calibration was released.


He said they are still driving it to make sure the light stays off when I talked to him yesterday. I didn't get a chance to ask about the date the calibration was released. If all goes well I'm picking the car up Saturday so I'll talk to him more about it then.


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## Goodluckgluck (Nov 13, 2021)

CEL came back on 5 miles after leaving the dealership. (shocker) Now they are saying it needs another EGR cooler. 

I did not ask about the release date for the latest update, it didn't fix anything.


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## Barry Allen (Apr 18, 2018)

Goodluckgluck said:


> CEL came back on 5 miles after leaving the dealership. (shocker) Now they are saying it needs another EGR cooler.
> 
> I did not ask about the release date for the latest update, it didn't fix anything.


Hard to guess with your car but my best guess would be the mechanic saw the firmware update I mentioned with the recall to fix the issue where the CEL wouldn't illuminate with certain problems, and they thought that new firmware version would fix your problem.


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## Barry Allen (Apr 18, 2018)

Goodluckgluck said:


> Now they are saying it needs another EGR cooler.


What is their explanation for that? Is the current one somehow broken?


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## Barry Allen (Apr 18, 2018)

It’s back again today with the three codes set:
P0401
P0403
P0405

This time the light came on the instant I started the car this morning. It didn’t illuminate in the middle of a drive - started and came right on.


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## Goodluckgluck (Nov 13, 2021)

Barry Allen said:


> What is their explanation for that? Is the current one somehow broken?


It has a cooler efficiency code. My guess is that it is plugged again. 

I only put 10,000 miles on it a year so it's either my driving habits or something it's creating too much soot.


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## Juan23 (8 mo ago)

oregon_rider said:


> yes. it is topside and easy to change the egr valve. I looked at the instructions on alldatadiy.com a while back - factory service manual info is on-line. The egr cooler on the other hand - that looked like a bit more work.
> 
> send me a private message with your e-mail and I can print out the instructions and send them to you.
> 
> ...


HI, I have this problem. P0401. I want to extract and clean the EGR valve.

Could I have a copy with the instructions? Thanks

[email protected]


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## Barry Allen (Apr 18, 2018)

The light turned off yesterday. That was quick. I expect it will be back again soon.


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## Cruz15 (Mar 17, 2016)

I had a TC show up, egr cooler efficiency didnt write it down. I looked at the intake hoses and both were a little loose, one was 1/8 and the other about 1/2 a turn. I tightened them up did a regen and drove around for an hour at 2000 rpm. It has not came back on. I think our cars are sending a lot of extra fuel in our engines even if there just a small air leak. Seems like a terrible thing to do. Will have to check my intake hoses on a regular basis permanently.


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## Barry Allen (Apr 18, 2018)

The light is on again!


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## Barry Allen (Apr 18, 2018)

It turned off today!


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## Barry Allen (Apr 18, 2018)

The light is on again!


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## Barry Allen (Apr 18, 2018)

It turned off today!


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## Barry Allen (Apr 18, 2018)

The light was on again today. Around 4am I had to relocate a raccoon I trapped at my parents' house and it turned on when driving the guy to his new home.










By this afternoon, when taking my mom on errands to a hair appointment and other things, it was off again.


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## Barry Allen (Apr 18, 2018)

Fun times this week. The morning of the 7th I had to relocate another raccoon I trapped. I backed the car out of the driveway and shut it off. By the time I got the trapped trash panda in the trunk I got an email from OnStar saying the emissions system needed servicing. Driving the car around that day resulted in nothing happening.

Then, today, the CEL comes on this morning. It's like I got a full 24-hour notice via email that the CEL was going to illuminate!


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## Barry Allen (Apr 18, 2018)

The light is back on again today! This was after driving through what was easily the biggest rain storm I've ever seen in my life (lots of roads and intersections flooded to about a foot deep of water). Today it was humid and I've noticed that after driving the car in very wet/humid weather, the light comes on. I think there is soot throughout the EGR system and when it's wet/humid the soot gets all chocked up and turns the light on. After some days of driving when it's hot weather to dry it out, the light goes off.


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## Barry Allen (Apr 18, 2018)

And now the light is off today. Doing more driving in hot weather has basically dried the car out and I think the soot is back to being dry and not clogging whatever is gumming up the EGR valve.


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