P0401 code with recently cleaned egr circuit

Discussion in 'Gen 3 Prius Technical Discussion' started by Delo404, Aug 10, 2019.

  1. Delo404

    Delo404 New Member

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    I recently got a p0401 code (EGR system flow is insufficient) but I cleaned the egr cooler, valve, and pipe as well as the intake manifold less than 10,000 miles ago, I know I got everything very clean. I do burn oil, maybe 1qt every 2,000 miles or so and I have a high mileage prius almost 280,000, but other than that it runs really well. From previous posts it seems like it could be the egr valve went out on me or the map sensor, anyone know how to figure out which of those it could be or what else it could be, I wouldn't think it would be possible for the egr cooler to clog in less than 10,000 miles.
     
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  2. Raytheeagle

    Raytheeagle Senior Member

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    You could always take the black cap off of the egr valve and manually actuate it just in case the valve has some sticksion ;).

    To get the screws off, use an impact screwdriver as they are dissimilar metals and you strip the head otherwise:cool:.

    Good luck and keep us posted (y).
     
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  3. Delo404

    Delo404 New Member

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    Just tried taking the cap off the valve, it moves freely, no stickyness at all.
     
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  4. Delo404

    Delo404 New Member

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    Cleaned the tpm sensor and cleared the codes I'll keep you guys posted if the code comes back or not.
     
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  5. 2011Prii

    2011Prii Junior Member

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    When you say you cleaned the tpm sensor, what exactly is that? I am battling this same issue immediately after a very thorough cleaning that I've done more than once to make sure that's not the issue. I cleaned the map sensor as well with no luck.
     
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  6. Delo404

    Delo404 New Member

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    I'm not sure what is the correct term for the sensor, but I think we are talking about the same sensor, I have seen people call it the map sensor as well as tpm, but it's the air pressure/flow sensor in the intake near the filter that I'm talking about, I cleaned it with crc mass airflow sensor cleaner and so far I have not had the light come back, but I have only driven about 5-600 miles since then and now I'm on vacation for a few weeks, I'll update after I get some more miles on it
     
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  7. Mendel Leisk

    Mendel Leisk Cloud Watcher

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    TPM is probably Tire Pressure Monitor, a red herring.
     
  8. Delo404

    Delo404 New Member

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    I probably am using the wrong term, but it's the intake airflow/pressure sensor that I'm talking about not the tire pressure sensor lol
     
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  9. Mendel Leisk

    Mendel Leisk Cloud Watcher

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    Underbars added in the above, to avoid Priuschat's every helpful nanny converting it to "nice person".

    Yeah CRC Mass Air Flow sensor is the one to use. I've also used in on the Manifold Absolute Pressure sensor.

    The Mass Air Flow sensor (MAF) is the up near the top, just beyond the engine air filter IIRC.

    The Manifold Absolute Pressure sensor (MAP) is just below and to the right of the throttle body (as you stand at front of engine). That's the one that looks like a little resistor.
     
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  10. Delo404

    Delo404 New Member

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    The sensor I cleaned is the one just beyond the filter so I guess that's the mass airflow sensor, if the map sensor is on the intake manifold by the throttle body I would have cleaned that when I cleaned the intake manifold and throttle body, which was about 10,000 miles ago now
     
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  11. Mendel Leisk

    Mendel Leisk Cloud Watcher

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    Yeah, I found the MAP sensor pretty much swimming in oil, when I did the intake cleaning. The MAF sensor on our I took a look at, and did clean, but it looked pretty much pristine.
     
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