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Discussion Starter · #41 ·
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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Discussion Starter · #43 ·
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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Discussion Starter · #44 ·
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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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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Discussion Starter · #47 ·
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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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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Discussion Starter · #52 ·
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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Discussion Starter · #53 ·
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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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.

This sounds like a total horse manure answer from them.
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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Discussion Starter · #55 ·
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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Discussion Starter · #56 ·
"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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Discussion Starter · #57 ·
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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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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