EGR Valve, 2012 Duramax

[JohnnyR]

I inadvertently posted this in wrong section. Belongs here:

Took my 2012 Duramax K3500 DRW in last week for the 3rd time to address regens that occur every 200 miles. last time, they replaced the DEF injector but no improvement. This time
they discussed with GM Tech and ultimately concluded EGR valve was staying open, and replaced it. Just got it back last Friday so cannot tell you whether this was succesfful yet. My question is"can anyone tell me how the EGR valve would affect regens of the DPF"? Does it make sense?

[Kennedy]

Knowing what I know about the earlier EGR systems and their tendencies to set DTC's for insufficient or excessive flow after only very minor alterations, I would expect that the LML would be every bit as picky or more.

That said, I've never had to diagnose the LML EGR system. I've had the system inoperative for quite some time now.

My take on the production of soot is that the timing has been retarded to reduce NOX and combustion temps so we see an increase in soot. An after treatment like DEF allows a bit more combustion temp allowing for cleaner burn and less soot. I'm not well enough versed to know what actual impact the DEF has on the soot that is produced, but it is my understanding that as an after treatment it is primarily just reducing NOX.

I'm still running 700 mile regens at 30g soot load +/- 5g which is the max miles that the programming seems to allow. I do use significantly more DEF as a result of the tuning and am investigating how to combat that.

[JohnnyR]

Mine never set any codes which confused me and the dealer. Nevertheless, I hope this fix works. Should have driven enough soon to say.

[JohnnyR]

Did not fix it. Still regens at 200 miles. Suggestions?Ttruck is back in the shop yet again.

[Kennedy]

Knowing what I know about the earlier EGR systems and their tendencies to set DTC's for insufficient or excessive flow after only very minor alterations, I would expect that the LML would be every bit as picky or more.

That said, I've never had to diagnose the LML EGR system. I've had the system inoperative for quite some time now.

My take on the production of soot is that the timing has been retarded to reduce NOX and combustion temps so we see an increase in soot. An after treatment like DEF allows a bit more combustion temp allowing for cleaner burn and less soot. I'm not well enough versed to know what actual impact the DEF has on the soot that is produced, but it is my understanding that as an after treatment it is primarily just reducing NOX.

I'm still running 700 mile regens at 30g soot load +/- 5g which is the max miles that the programming seems to allow. I do use significantly more DEF as a result of the tuning and am investigating how to combat that.

More follow up to my comments that would seem to support my understanding that the DEF does not reduce emissions, it allows for tuning that creates more NOX and less particulate then treats the NOX on the back end:

"Because SCR deals with NOx outside the engine, manufacturers are once again able to tune their engines to run more efficiently and produce more power. The increase in engine efficiency also leads to a reduction in particulate matter, resulting in less frequent regeneration of the DPF and adding to the increased fuel economy. "

Read more: http://www.trucktrend.com/how-to/expert-advice/1402-understanding-diesel-exhaust-fluid-basic-training/#ixzz3c6wpNRWY


The tuning work that I have done further increases the NOX and cleans up the burn extending the regen cycle and using more DEF depending on the level of the tuning.

[JohnnyR]

Replacing EGR valve did not help. Took it in again last week for something else and Dealer checked system again and can't find anything wrong. Still regenning at 200 miles. Anyone else have any ideas.

[a5150nut]

JohnnyR,

Mr. Kennedy probably has the most in depth knowledge of your problem. I wouldn't be so quick to dismiss what he is telling you. Unless your just looking for a quick easy fix that won't cure your problem.

[JohnnyR]

A5150nut,
I certainly am not discounting J Kennedy's opinion. Just frustrated that GM seems unable to correct the problem.

[CoyleJR]

Do you have a modified air filter or air intake system? There was someone last year that posted a similar regeneration issue to yours. He indicated that his truck was stock other than the air filter system. I believe that GM voided his warranty and he was very upset. If your truck is modified I would try returning it to stock and see it it fixes the problem.

Good luck
John

[JohnnyR]

CoyleJR
Everything is stock.