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Need help diagnosing P0AFC

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by SB6, Dec 3, 2022.

  1. SB6

    SB6 Member

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    Well... I put it together this week, and I'm getting P308A. Car won't go into ready mode. It's reading like every other cell as 0V. Did I hook something up wrong? Is the replacement voltage sensor actually incompatible? Or did I actually kill the battery by leaving the car unstarted for a couple weeks?

    I'll rescan and post codes/data in a bit when I get back home to the car
     
  2. SB6

    SB6 Member

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    Here are the DTCs and data:



    [​IMG]

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    [​IMG]
     

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  3. ChapmanF

    ChapmanF Senior Member

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    That does seem like either an "incompatible" voltage sensor unit (if there are incompatible ones—I don't know), or just simply a busted one. How was it obtained?
     
  4. SB6

    SB6 Member

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    Only reason I considered it possibly incompatible is because it has a slightly different part number (#89892-47080/175100-7280, board #175131-7280) than my existing one was. There are pictures in this thread, post #31 and #36.

    I'm wondering if it might be something like 2012-2015 use a different sensor than 2010-2011? I hadn't thought something like this could be an issue, since they're still the same generation.

    As for how it was obtained, I bought it from a used hybrid parts seller on eBay.

    I'm not sure what my next steps are. I'm thinking to remove the #2 frame wire and check continuity between each voltage sense wire and the corresponding pin on the connector. Sounds like it'll be time-consuming... But if that checks out then next I guess I'll swap back my old voltage sensor and see if there's any change.
     
    #44 SB6, Jan 22, 2023
    Last edited: Jan 22, 2023
  5. ChapmanF

    ChapmanF Senior Member

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    A little tedious, but it goes pretty quickly, just 15 to check.

    The very regular pattern, exactly every other reading zero, has me thinking more of some kind of problem on the sensor board though. It would be a pretty weird thing to happen to a bundle of fifteen wires.
     
  6. SB6

    SB6 Member

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    Can you think of any possibility of me connecting something incorrectly while putting the bus bars/sensor/junction block back together, which might result in this?
     
  7. ChapmanF

    ChapmanF Senior Member

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    Not easily.
     
  8. SB6

    SB6 Member

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    Uhh. Looking at it again in the daylight, it looks like I neglected to notice missing "bus bars" on the replacement frame wire... That'll probably be why I'm getting the uniformly weird voltage readings.

    Looks like I stripped a couple nuts on while installing, so I gotta go grab my friend's extractor socket again, before I can reinstall with bus bars.

    I hope I didn't damage any of the blades by torquing directly onto the blades rather than onto a bus bar...

    Also the 12V finally gave out, so I'll have to fix that too.
     
  9. ChapmanF

    ChapmanF Senior Member

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    Yup, that'll do it. Also makes it hard for the electrons to get from one end of the battery to the other.

    I didn't think that was the way no.2 frame wires were sold.

    But then, for Gen 3, they aren't sold ... so whoever sold it to you must have just harvested the bars from it first.
     
  10. SB6

    SB6 Member

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    Will submerging the bus bars in vinegar harm them at all? Wouldn't think so, but just making sure, before I do that to try to clean my old ones
     
  11. ChapmanF

    ChapmanF Senior Member

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    You wouldn't be the first to do it that way. Should be fine.

    I would rinse them well afterward.
     
  12. ASRDogman

    ASRDogman Senior Member

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    Baking soda and water works well, with a tooth brush, or brass brush.
    Rinse very well, and dry them.

     
  13. SB6

    SB6 Member

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    Weird question maybe, but would I be able to jump the car with the 12V disconnected, so I can pop the trunk without crawling over the open hybrid battery area? Or would it be an open circuit and not do anything?
     
  14. ASRDogman

    ASRDogman Senior Member

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    Hook up the jumper, or jump box the to location in the fuse box,
    then you should be able to unlock the car with the key, or the switch on
    the drivers door.

     
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  15. SB6

    SB6 Member

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    For anyone else that was wondering, I just wanted to confirm that I was able to pop the trunk with a portable jump pack connected under the hood, even while the 12V battery was removed. I did have to put the jump pack into boost mode.

    Anyways, I cleaned my old bus bars and put them on, hooked up all the connectors, and the car starts up now. Cleared my codes, and no DTCs remaining! Even the brake booster codes are gone.

    Now I just have to put all the covers and stuff back on. Debating leaving it open, as I might try to tackle cleaning the fan/vent this weekend. I don't think it's dirty, but might as well, if I do have the time. But I need to put it together enough to be able to drive it safely and without losing any nuts/bolts/pieces I have lying around from disassembly.
     

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  16. tedrotedro

    tedrotedro New Member

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    Hi @SB6 – I came across this thread while trying to troubleshoot my check hybrid system P0AFC code. It sounds like I have precisely the same issue as yours with two side by side battery cells reading 0V and 25V. I reviewed all of the content in this thread and wanted to confirm that the fix to the issue was indeed a new "battery smart unit" / "battery pack sensor module"?
    I know there were some other issues encountered during your journey on this repair but it seems ultimately this was the faulty part that needed replacing is that correct?
    Thank you!
    Ted
     
  17. SB6

    SB6 Member

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    Yup, I changed out the smart unit and was good to go. I also cleaned the bus bars and brushed off the studs on each cell, but that's more of preventative maintenance, I don't think related to the P0AFC code
     
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  18. tedrotedro

    tedrotedro New Member

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    Hi @SB6 – I came across this thread
    Awesome thank you!