How do you run the Notorious Check Engine P0401 - EGR System Insufficient flow , out of Town ? ! (1 Viewer)

Joined
Apr 17, 2018
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Pensacola, FL
As someone who went through this (and thinks he is done), one of the most common culprits is the EGR VSV - if your mechanic didn't replace that, I'd start by testing it. Lot of info available on it including here Checking VSV for EGR easy way P0401 - https://forum.ih8mud.com/threads/checking-vsv-for-egr-easy-way-p0401.211364/
This. I just had my upper intake off and replaced all my vac lines and any other worn/cracked components under the intake manifold. The EGR VSV (blue/green one) was toast. New one got rid of the CEL that has been present for 2 years. I've driven about 1000 miles since the repair with no CEL and no further issues. Hope you get 'er fixed.

Edit: make sure you test the vsv's per the service manual. Those tests will either save you a few hundred dollars in parts or give you peace of mind about which parts need replacement.
 

FreedomRider

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Nov 7, 2020
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Smithville,NJ
This. I just had my upper intake off and replaced all my vac lines and any other worn/cracked components under the intake manifold. The EGR VSV (blue/green one) was toast. New one got rid of the CEL that has been present for 2 years. I've driven about 1000 miles since the repair with no CEL and no further issues. Hope you get 'er fixed.

Edit: make sure you test the vsv's per the service manual. Those tests will either save you a few hundred dollars in parts or give you peace of mind about which parts need replacement.
Thank you for sharing your experience and the good advice. I will let everyone know what the solution was once resolved. Best Regards, Joe
 
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Loomis, Ca
Gotta take off the upper manifold, clean it and replace VSV and all vacuum lines and parts associated with it that are on the underbelly of manifold...this solved my PO401
 

FreedomRider

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Nov 7, 2020
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Smithville,NJ
Gotta take off the upper manifold, clean it and replace VSV and all vacuum lines and parts associated with it that are on the underbelly of manifold...this solved my PO401
Woodsman , thank you ! it's in the dealership with an old school 80's mechanic who is doing just that , will keep you posted . best regards, Joe
 

FreedomRider

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Nov 7, 2020
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Smithville,NJ
Gentleman ,
Thank you all for the excellent advice as the Check Engine P0401 has been run out of town and hopefully never returns!
God bless you all for your time and support in helping me resolve this issue! Joe

Issue
My '97 LC failed NJ State Inspection due to a not ready ODB System status for the Catalytic Converter , Oxygen Sensors-Heater and EGR Systems .
Per the Toyota Technician the truck did not fail due to a 401 Code , but because the above three systems were not completed in the monitoring system 1-11.
The Technician determined the EGR Valve and passages were operating properly and the vac control valve, tvv, modulator and check valve all tested good.

Solution
  1. Removed and Replaced the Intake Manifold cleaned the Throttle Body
  2. Replaced the Intake Manifold , Throttle Body , EGR Valve and EGR Inlet Gaskets
  3. Replaced all EGR Vacuum hoses
  4. Replaced coolant hoses from the throttle body
  5. Secured the EGR VSV to the underside of the manifold
  6. Replaced breather hose ****See attached files for additional details****
 

Attachments

  • Code P0401 Assessment.pdf
    1.8 MB · Views: 4
  • P0401 Solution.pdf
    1.7 MB · Views: 8
  • NJ STATE INSPECTION REPORT.pdf
    1.1 MB · Views: 2

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