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Old 07-12-2011, 09:34 PM
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How does the computer know EGR is not flowing

So I see that plugging the EGR cooler to look like it is functional and leaving the EGR plugged in can still throw a code about EGR flow low or something like that. How does the ECM know the flow is low? There's no flow meter or anything so how does it do it Intake air temp or something?

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Ira
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Old 07-12-2011, 09:52 PM
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You just asked the million dollar question.

I always wonder if you could just solder in a resistor somewhere to read good values.
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Old 07-13-2011, 06:58 AM
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Quote:
Originally Posted by SandawgK5 View Post
So I see that plugging the EGR cooler to look like it is functional and leaving the EGR plugged in can still throw a code about EGR flow low or something like that. How does the ECM know the flow is low? There's no flow meter or anything so how does it do it Intake air temp or something?

Thanks

Ira
IAT2 monitors temp in the intake manifold. I would expect there to be a rise in temp when the EGR is commanded to open. I don't know of any other sensor it might be looking at.
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Old 07-13-2011, 07:09 AM
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Originally Posted by PGreenSVT View Post
IAT2 monitors temp in the intake manifold. I would expect there to be a rise in temp when the EGR is commanded to open. I don't know of any other sensor it might be looking at.
That plus a drop in exhaust back pressure measured by the EBP sensor, which (for the OP) also controls the vanes on the turbo, so any resistor modification would cause your turbo to not function correctly. In order to "fix" it, you must run custom tuning.
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Old 07-13-2011, 08:29 AM
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Originally Posted by Evil Eye View Post
That plus a drop in exhaust back pressure measured by the EBP sensor, which (for the OP) also controls the vanes on the turbo, so any resistor modification would cause your turbo to not function correctly. In order to "fix" it, you must run custom tuning.
Of course. Thanks Shawn.
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Old 07-13-2011, 10:20 AM
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and i belive that when the egr is command to open, that point through airflow meter isn't the only place where the air goes to the engine...
that might make some confusion to the pcm... i mean if the airflow thru air flow meter doesnt change at all when egr is command to open because of egr delete.
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Old 07-13-2011, 10:40 AM
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From what I understand the PCM sees that all perameters are met for EGR function, open EGR valve a certain% then the PCM knows it opens because of a position sensor in the EGR valve. Then the PCM monitors EBP and MAP pressures to make sure that the valve opened and that the exhaust gas is flowing thru the cooler into the intake. MAP and EBP will change dramatically when the EGR valve opens and closes.
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Old 07-13-2011, 12:45 PM
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Originally Posted by juzatheman View Post
and i belive that when the egr is command to open, that point through airflow meter isn't the only place where the air goes to the engine...
that might make some confusion to the pcm... i mean if the airflow thru air flow meter doesnt change at all when egr is command to open because of egr delete.

My truck doesn't have a MAF so maybe that isn't too big a deal?
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Old 07-13-2011, 04:59 PM
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Sounds like a bullet proof EGR cooler is in my future then I am moving back to Cali and can't have any codes and they check for EGR function. Has anyone that has switched to ELC had stock oil cooler issues? Is the bullet proof air to oil cooler necessary?

Dik
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Old 07-13-2011, 07:38 PM
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Isn't there a butterfly valve in the egr system on 05 and up motors that will track egr flow?
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