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P0404

  • autojoe
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11 Feb 2019 12:35 #26966 by autojoe
P0404 was created by autojoe
Can excessive exhaust back pressure cause egr codes and a no start from excessive exhaust back pressure? Thanks

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  • chief eaglebear
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11 Feb 2019 13:27 - 11 Feb 2019 13:29 #26969 by chief eaglebear
Replied by chief eaglebear on topic P0404
I would say yes since a bad backpressure problem would heat catylyst excessively the egr is designed to opersye based on cylinder/exhuast temperature if a backpressure is cuasing the engine to go through abnormal warm up/heating cycle it could fool the egr to operate at wrong time
Last edit: 11 Feb 2019 13:29 by chief eaglebear.
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  • Tyler
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11 Feb 2019 13:35 #26970 by Tyler
Replied by Tyler on topic P0404
Definitely can. But, the amount of backpressure needs to be extreme. Observing the MAP sensor during cranking would be a good direction test for this.

GM's can throw EGR codes with plugged converters because the amount of backpressure can actually lift the pintle off it's seat when the PCM didn't command it to. Or, the pintle will move more than commanded, for the same reason.
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11 Feb 2019 16:32 #26976 by autojoe
Replied by autojoe on topic P0404
Thanks for the replies.

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14 Feb 2019 08:05 #27037 by Doc n2mx
Replied by Doc n2mx on topic P0404
HI,
You state that the code you have is P0404
do you have any other codes? If not you need to look at what the code is telling you.

You did not state what this vehicle is so I am going with the generic code description.
P0404 states Exhaust gas recalculation circuit range /performance.

This tell me to be looking at the electrical circuit .
I would test all the wires make sure that you don’t have a bad connection opens or shorts. I would also lookup the EGR system and see what other components there might be such as a temp sensor .

You need to test all inputs and outputs in the circuit and dont for get the PCM check all the wires and powers and grounds..

Don't go down the rabbit hole looking for back psi and other things the code is there to help you focus on the problem (a starting point )..


Good luck
a scope would be a good tool to get your hands on


Doc

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