Please tell me, what should the ECU data flow and EGR be like?

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by wukong sun, May 7, 2025 at 6:26 PM.

  1. wukong sun

    wukong sun New Member

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    Does this mean the EGR valve is stuck?

    Idle, maintenance mode, let the water temperature rise, the cooling fan starts running, and the EGR data does not change

    f386dd96347f82218acde09dd5425a0.jpg
     
    #1 wukong sun, May 7, 2025 at 6:26 PM
  2. wukong sun

    wukong sun New Member

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    What is your normal data?
     
    #2 wukong sun, May 7, 2025 at 6:33 PM
  3. wukong sun

    wukong sun New Member

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    EGR Valve Position/Duty Cycle:
    At idle and low load: The EGR valve is normally partially open, allowing a small amount of exhaust gas to recirculate into the intake manifold to lower combustion temperatures and reduce the production of nitrogen oxides (NOx). You may see a non-zero percentage or a value indicating that the valve is partially open.
    At high load and acceleration: The EGR valve is normally closed. At this time, as much fresh air as possible needs to enter the engine for maximum power output. You may see a duty cycle close to 0% or a value indicating that the valve is closed.
    When cruising: The EGR valve may open moderately depending on engine load and speed.
    When accelerating hard or at full throttle: The EGR valve should be fully closed.

    For the 2014 Toyota Prius, here are a few things to keep in mind:
    The hybrid system in the Prius may have a specific control strategy for the operation of the EGR system.
    Carbon deposits are a common problem in the Prius EGR system, especially at higher mileage. Carbon deposits can cause the EGR valve to stick or the EGR passage to become clogged, which can cause EGR_ERR related fault codes.
    When you see EGR_ERR, it usually means that a diagnostic is needed to determine the specific cause of the problem. Diagnostics may include:
    Reading Trouble Codes (DTCs): An OBD-II scanner can provide more specific fault codes to help narrow down the problem.


    Common EGR related fault codes include

    P0401 (not enough EGR flow),
    P0402 (too much EGR flow),
    P0403 (EGR circuit fault), etc.

    Check the EGR valve: Check if the valve is sticking and if it can move smoothly.
    Check the EGR passage: Check if there is any blockage due to carbon deposits.
     
    #3 wukong sun, May 7, 2025 at 6:58 PM
    Last edited: May 7, 2025 at 8:30 PM
  4. Tombukt2

    Tombukt2 Senior Member

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    You can see the flow in HG in Toyoda software.
     
    #4 Tombukt2, May 7, 2025 at 7:29 PM
  5. Brian1954

    Brian1954 Senior Member

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    Where did you get the information from that you wrote in your post?

    At idle, the EGR is fully closed on the Prius.
     
    #5 Brian1954, May 7, 2025 at 7:49 PM
  6. wukong sun

    wukong sun New Member

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    I only have a small OBD device.
     
    #6 wukong sun, May 7, 2025 at 7:56 PM
  7. wukong sun

    wukong sun New Member

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    This is what I found on Google. I don't know what the value should be, so I'm posting this to ask for advice.
     
    #7 wukong sun, May 7, 2025 at 8:03 PM
  8. Brian1954

    Brian1954 Senior Member

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    The information that you found on Google is not correct.

    If you are looking at live data for the EGR valve when the engine is idling, you will not see any change in the data because the EGR stays closed at idle.

    What are you trying to do with the EGR?
     
    #8 Brian1954, May 7, 2025 at 8:21 PM
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  9. Tombukt2

    Tombukt2 Senior Member

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    You'll get that taken care of at some point
     
    #9 Tombukt2, May 7, 2025 at 10:04 PM
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  10. wukong sun

    wukong sun New Member

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    EGR_ERR: This data is the difference between the expected EGR and the actual EGR
     
    #10 wukong sun, May 8, 2025 at 1:47 AM
  11. Brian1954

    Brian1954 Senior Member

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    I have no idea what your scan tool is showing for the EGR data. Maybe someone else can help you.
     
    #11 Brian1954, May 8, 2025 at 8:42 AM
  12. ChapmanF

    ChapmanF Senior Member

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    That scan tool seems not to even know what kind of a car it is talking to. A gen 3 Prius does not report EGR information in that way.

    Perhaps there is some way to get that tool to show the result of the mode 6 noncontinuous monitor (module ID 0x31 test ID 0xBD) that the Prius uses. It should look like examples you see in this thread.
     
    #12 ChapmanF, May 8, 2025 at 8:54 AM
  13. Mendel Leisk

    Mendel Leisk Senior Member

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    You’ve got 3 threads going now, essentially the same topic. You’ve got a recently acquired 3rd gen, it’s got over 200k miles:

    Help Engine shaking and abnormal noise are not EGR problems | PriusChat

    Next post you disclose code P0301.

    I’d start checking for head gasket failure, and cleaning EGR system, in that order. More info in my signature (on a phone turn it landscape to see signatures).
     
    #13 Mendel Leisk, May 8, 2025 at 9:03 AM
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  14. Brian1954

    Brian1954 Senior Member

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    The scan tool that he is using is a very basic, generic, inexpensive one that I did an online search to get some information about. I could not find who the manufacturer is. It is a generic scanner made in China.
     
    #14 Brian1954, May 8, 2025 at 9:23 AM
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