Prius 2010 check engine code: P0101: Mass or Volume Air Flow Circuit Range/Performance

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by cb_jimmy, Feb 21, 2020.

  1. cb_jimmy

    cb_jimmy Junior Member

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    Hello Priuschat, I wonder if anyone has any idea how to fix code check engine code P0101. It has been repeatedly coming on and off in my prius for months. For driving, I couldn't tell any different. What i did to try fixing the code were:

    -replacing Engine air filter

    -replacing Mass Air Flow sensor

    -replacing wires harness

    -trying a different ECU module

    However, it is still coming back. What do I need to do to kill the code for good?
     
  2. ChapmanF

    ChapmanF Senior Member

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    There are eight pages in the Repair Manual (more info) on troubleshooting that code. As always, you could get a sensor code because something is off about the sensor (the conclusion many people jump to) or because something is off about what the sensor senses (in this case the amount of intake airflow compared to what's expected for the engine load). That could lead to exploring for intake leaks, EGR stuck open, etc. It'll probably be faster / more satisfying to follow the troubleshooting steps in the manual and just find where the problem is and fix it, than to keep swapping parts.
     
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  3. cb_jimmy

    cb_jimmy Junior Member

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    Thank. Not sure whether my local technicians can understand the repair manual (i'm living in a developing country and most technicians here have no formal training and cannot read English) but I will try showing them the manual.
     
  4. Rebound

    Rebound Senior Member

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    This type of error is very basic in engines these days. It’s not Prius-specific at all.

    The car’s computer measures how much air is entering the engine using two sensors: MAP and MAF. The MAF sensor is at the top of your air intake, on the top of the air filter housing. Make sure the electrical plug is attached, for starters. You can clean it, but it probably doesn’t need to be cleaned or replaced.

    After combustion, one or two oxygen sensors measure the oxygen in the exhaust, to determine the fuel trim level — do we need more or less air to fuel. You can use your scan tool to view the short term and long term fuel trim levels, which can help you troubleshoot. Vacuum leaks can cause these errors — a dipstick not fully inserted, or a bad o ring on the dipstick, for instance. Prius doesn’t have a lot of other vacuum leak vectors, though. No vacuum hoses at all.

    There are a lot of YouTube videos about this. i like the Schrodinger’s Box videos.
     
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  5. Grit

    Grit Senior Member

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    Don’t walk, run away.
     
  6. TMR-JWAP

    TMR-JWAP Senior Member

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    Don’t walk, run away.

    To where?

    I think the concern about understanding the repair manual link was that it is written in English. Does Phnom Penh, Cambodia have an English speaking or reading Toyota repair facility to try? Maybe an area that has a very large tourist population? If you can find a Toyota place, maybe they can at least do a good diagnostic.
     
    #6 TMR-JWAP, Feb 21, 2020
    Last edited: Feb 21, 2020
  7. ChapmanF

    ChapmanF Senior Member

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    Does Toyota have another online site with a different translation of the manuals?
     
  8. Elektroingenieur

    Elektroingenieur Senior Member

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    I’ve listed all the public or subscription websites I know about on the Wiki page; there are other websites accessible only to Toyota dealers and distributors.

    As far as I know, Toyota prepares only one translation for each language; I’ve never seen a Toyota service document in Basic English or ASD-STE100 Simplified Technical English, for example. I don’t know if a Khmer version of the third-generation Prius Repair Manual exists, but I doubt it, since the Toyota distributor in Cambodia doesn’t seem to sell new Prius cars.
     
  9. Rebound

    Rebound Senior Member

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    This problem is NOT about Toyota!
    All modern engines have this issue: This is basic engine management used by Toyota, GM, Nissan, Ford... everybody.
     
  10. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    I see part of the troubleshooting for P0101 is to check the condition of the EGR system. Since that's a known-to-clog factor, maybe check that. Note too, the bulk of the troubleshooting involves use of Toyota proprietary Techstream software.

    How many miles on it btw?

    EGR info follows (and some attachments):

    The simplest way to see where you're at, is to check the degree of carbon build up in the EGR pipe, a stainless steel connecting pipe between the EGR valve and intake manifold. Watch @NutzAboutBolts video #16 here:

    Nutz About Bolts Prius Maintenance Videos | PriusChat

    Two or three other videos linked there too, for the full cleaning of the intake manifold, full EGR clean, and Oil Catch Can install.

    Good thread:

    EGR & Intake Manifold Clean Results | PriusChat

    Another:

    Oil Catch Can, Eliminate that knock! | PriusChat

    Some tools worth having:

    E8 Torx socket (mandatory)
    E6 Torx socket (optional, but good to have, to remove the throttle body studs from intake manifold)
    3/8" ratchet wrench, regular and long handle, flex head, you can never have enough (or 1/2 plus reducer)
    1/4" ratchet wrench, or 3/8" to 1/4" reducer
    Ratchet extensions: you can never have enough
    Long needle nose piers, straight and bent tip
    Ratcheting 12mm box wrench (optional, but makes disconnection of the EGR cooler from exhaust easier)
    Torque wrench (3/8" and 1/4" both good to have)
    Floor jack and safety stands (or ramps): basically some method to raise front, if you need to take underpanel off, which you may need to, both for access and to recover dropped items.
     
    #10 Mendel Leisk, Feb 21, 2020
    Last edited: Feb 21, 2020
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  11. ChapmanF

    ChapmanF Senior Member

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    By the same token, in a twist on a favorite PriusChat theme, in this case it is about checking for a valve stuck open and supplying too much EGR.
     
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  12. cb_jimmy

    cb_jimmy Junior Member

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    We have Toyota authorized dealer here with their maintenance facility. They don't bring Prius though. And since their facility can get pricey, I prefer exploring other options first.


    Wow, thank for the links. They're very informative.

    My prius is on her 60k miles.

    The check engine code had cleared itself again yesterday and hasn't come back yet after several driving sessions today. When it's back, the next things I'll try, based on the inputs in this thread, are the inspection of vacuum leak, EGR valve, and throttle body.
     
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  13. Rebound

    Rebound Senior Member

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    Most check engine codes require three full Startup/Warmup/Drive/Shut down cycles until they make the CEL come on. As I’ve said, there is nothing Prius or hybrid-related about this error. Every gas-powered car sold today can have this error.
     
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  14. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    The CEL can also take multiple start up before it'll go away I think. In other words, after trying something to resolve the issue, give it a while, the CEL may persist for the next while, even though you've solved the problem.
     
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