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Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!

P0404

  • autojoe
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7 years 1 month ago #22174 by autojoe
P0404 was created by autojoe
2002 gm impala 3.8 hesitation problems. New egr valve. Disconnected battery to clear pcm closed egr learned value. Codes comes back hesitation still there. Would some kind of combustion issues cause this code and hesitation? Excessive back pressure?

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  • Tyler
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7 years 1 month ago #22179 by Tyler
Replied by Tyler on topic P0404
Excessive backpressure can definitely cause this code. The hesitation, too. That year of Impala have cats plug all the time.

Next easiest move would be to pull the EGR valve again, plug thr intake port, and use a vacuum gauge on the exhaust port. More than 2 PSI is a problem.

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7 years 1 month ago #22184 by autojoe
Replied by autojoe on topic P0404
Thanks Tyler I never ran into the excessive back pressure for this code but was leaning towards it. Appreciate it. Joe

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