P3190 & P0420 - Sudden Limp Mode (P0A0F) On Freeway

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by SCBPrius, Mar 12, 2025.

  1. SCBPrius

    SCBPrius New Member

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    Long-time forum lurker, and now have something worthwhile to query about.

    2012 - Prius Two - 310k miles
    Engine replaced at ~185k for standard headgasket issue
    Fuel Pump Replaced at ~280k miles

    Vehicle has had a sudden & intermittent check hybrid system warning light and kicked into limp mode, this has historically occurred (2-3 times) and while on the freeway, driving at freeway speeds. Only codes showing were P3190, P0420 and P0A0F. Second code is likely related to clogging cats (they are original) so my focus had been on P3190 as I thought P0A0F was a generic hybrid error code (caused by the P3190).

    I've dug into things slightly, and the throttle body had some carbon buildup, but wasn't totally covered, and because this issue has occurred while under freeway drive load, this didn't seem likely to be the issue. Also checked the EGR ports inside the intake manifold, but they were unclogged and looked relatively clean as well.

    Checked under oil cap for any signs of headgasket issue, and I don't appear to be using any coolant (yet), though the exhaust does potentially smell a bit rich.

    After the tow, and clearing the P0A0F it starts up and drives, but there's obviously something which caused the P3190. Any suggestions for likely culprits? I wondered if it could be the Fuel Pump again, shop might have used a "budget but OEM spec" option that time... My searching on the forum corroborates my guestimate about the fuel pump being the issue, but seems surprising it would fail that quickly.

    Would appreciate any guidance!
     
  2. MAX2

    MAX2 Senior Member

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    P0A0F
    If an engine malfunction occurs, an engine malfunction signal is the ECM to the power management control ECU (HV CPU) . When the power management control ECU (HV CPU) receives this signal, it sets a DTC and performs fail-safe control.

    This error code has subcodes that could be read in a workshop with a special scanner. Subcodes could accurately indicate the source of the problem.

    But in general, yes, while driving, these could be problems with fuel supply, clogged filters and problems in the fuel pump.
    I would not exclude a small amount of fuel remaining in the tank.
     
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  3. ChapmanF

    ChapmanF Senior Member

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    That's pretty much right. P3190 is set by the Engine Control Module, the ECU that has direct responsibility for the engine. P0A0F is set by the power management control ECU, which is kind of the orchestra conductor for the car. It said "hey ECM, I'll crank the engine now if you'll make it go", and cranked it, but it didn't go, and the P0A0F kinda means "I don't know what the story is, but I asked the ECM to make the engine go and that didn't happen."

    So P3190 is the information you've got from the ECM, which is in the best position to know. But people are still frustrated that P3190 is not a more specific code. It means "hey, I calculated how much torque the engine should be making right now but it's making less than a fifth of that", which tells you the engine is running like cr@p for sure, but doesn't tell you a lot about why.

    It's one of those deals where a lot of different things can make a gasoline engine run like cr@p, and the human has to kind of dust off the old gasoline-engine diagnosis cap and start checking them all off the list.
     
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  4. SCBPrius

    SCBPrius New Member

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    Thank you!

    On most recent instance, fuel was filled to top (by me) that morning at the "regular" gas station we use for all our vehicles, so that aspect is likely ruled out.

    Dr Prius app and a Veepeak bluetooth OBD2 code reader wouldn't give the required additional color (the degree of detail) on those codes which you mentioned, right? I presume that would require a more professional Autel level type tool?

    If so, I'm effectively at the point where I either, 1) throw parts at it and hope I get lucky, or 2) get a real shop to do some diagnostic work
     
  5. SCBPrius

    SCBPrius New Member

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    Yes, my automotive diagnostic cap has effectively reached its knowledge and experience limit with how much I've done to this point, and without additional data from a more advanced scan-tool, it seems there's not much more I can personally do other than throw parts at it and guess.
     
  6. MAX2

    MAX2 Senior Member

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    Trying to replace random hardware is a bad idea.
    Error code P3190 can have many problem areas. A more advanced scanner is needed that can read freeze frame data when an error is recorded and narrow down the suspects based on this data.
    This is directly indicated in almost half of the cases of error occurrence.

    Tech Tips
    Read freeze frame data using the intelligent tester. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can be helpful in determining whether the vehicle was running or stopped, whether the engine was warmed up or not, whether the air-fuel ratio was lean or rich, as well as other data recorded at the time of a malfunction.
     
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  7. SCBPrius

    SCBPrius New Member

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    This attached PDF is what I was able to pull from my recently acquired Autel AP200 when the error last occurred. I'm new to this granularity of data, but beyond the higher Catalyst temp values, I didn't see anything which jumped out at me as a problem when I tried googling the dataset.

    Does anything look particularly out of spec to anyone?

    The original listed error codes were the only ones found in any system after the full-scan with the AP200.
     

    Attached Files:

  8. Brian1954

    Brian1954 Senior Member

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    I also do not know what all the data from the freeze frame means, but there are no misfires reported, and the short and long-term fuel trims look good. So I am guessing that rules out any problem with the fuel pump.
     
  9. MAX2

    MAX2 Senior Member

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    It is not quite clear what this error is. What is the error number?
    Does Autel give a list of frozen parameters for each error when this error occurs?
    Is there a subcode indicating the problem area?
    Using Techstream, everything is more detailed there. List of systems, list of errors, freeze frame data.
    [​IMG]

    [​IMG]
     
    #9 MAX2, Mar 24, 2025
    Last edited: Mar 24, 2025
  10. SCBPrius

    SCBPrius New Member

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    For completions sake, and for other users in the future: ultimately I was able to get the vehicle to fail with the same two trouble codes, while on side-streets and read detailed subcodes for the P3190, which was showing subcode 204.

    There are technical document pdfs attached on some posts on these forums showing the diagnostic process with the above conditions. Based on everything the vehicle was exhibiting and the fact that Fuel Pump is one of the first items to check in that diagnostic recommendation document, (and the fact the Fuel Pump was replaced by a shop nearby with a budget option a year ago) I decided to replace the Fuel Pump myself without additional testing.

    I bought a genuine Denso (which is OEM brand I believe) fuel-pump and it literally took 30 minutes to replace, anybody can do this, it's quite easy, especially with youtube videos showing the process. Do not waste money on this job, the book time is just criminal.

    As of today, the vehicle has traveled ~80 miles without tripping codes again, and I strongly believe this may have been the solution. After installing the fuel pump, the car also felt a bit more "peppy" so another indication that it's properly sorted. The Lesspn: Don't cheap out, get the Denso fuel pump for replacement.

    Vehicle still shows the P0420 (which is either clogging/end of life CAT, or the upstream O2 sensor) I'll try replacing the O2 sensor before looking for a secondhand cat off a damaged vehicle in SoCal.

    Thanks all for your assistance!
     
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  11. Mendel Leisk

    Mendel Leisk Senior Member

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    #11 Mendel Leisk, Apr 7, 2025
    Last edited: Apr 7, 2025