Hvmodules all the same voltage. Bad?

Discussion in 'Gen 2 Prius Technical Discussion' started by Davethewave, Mar 9, 2022.

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  1. Davethewave

    Davethewave Junior Member

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    Noticed car engine running and stopping quickly while stopped.
    Next day red triangle. P0A80 code.
    Using torque, all voltages the same and good. 16.9 to 17.
    Drove car (with triangle check engine on)without issue a few miles and then went into slow mode. Got code p3021.
    I had replaced some modules years ago but it was easy seeing the weak modules. Now no variation in voltages.
    Does this sound like the hv ecu?
    I am in humid Florida any ideas? Thanks in advance.
     
    #1 Davethewave, Mar 9, 2022
  2. davecook89t

    davecook89t Senior Member

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    Your code scanner will not generally lie (although it may miss some codes if it is not fully hybrid compatible). Code P3021 translates to Block 11 being weak, so either or both of Modules 21 or 22 (numbered from the opposite side from the ECU) will need to be replaced. Nominal voltages with the car sitting still don't tell you much. Under load, the weak modules reveal themselves. Hybrid Assistant or Torque Pro have facilities for tracking block voltages over time as the car is put through its paces. That is where you would expect to see significant voltage differences between the blocks. Certainly corrosion could be a problem anywhere on the battery or ECU, so it's worth giving a thorough inspection when you have the cover off, but a corrosion problem is not indicated by P3021.
     
    #2 davecook89t, Mar 9, 2022
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  3. ericbecky

    ericbecky Hybrid Battery Hero

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    Check corrosion on those wire, ring terminals.
    Also recheck the torque value you made for all the nuts.
    You should have used an inch-pound torque wrench to set them all to 48-inch pounds.
     
    #3 ericbecky, Mar 10, 2022
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  4. Davethewave

    Davethewave Junior Member

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    My first mistake was miss interpreting code. 2nd was watching modules while driving. With ice running all voltages were good.
    This morning waited till I could move car under battery. Sure enough block 11 showed weak.
    I want to mention Matt at Texas Hybid Batteries. So very helpful. He called me back quickly. Discussed patiently. Never tried to sell me.
    Thank you to all that took the time to help.
     
    #4 Davethewave, Mar 10, 2022
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  5. Davethewave

    Davethewave Junior Member

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    I replaced a module last year. Car lived in a dry garage till we got it. I was amazed at the amount of corrosion on studs and bus bars. Is it ok to smear dielectric grease on connections?
     
    #5 Davethewave, Mar 11, 2022
  6. Davethewave

    Davethewave Junior Member

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    Pics of corrosion
     

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    #6 Davethewave, Mar 11, 2022
  7. mr_guy_mann

    mr_guy_mann Senior Member

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    Yep, you can bury the connections in (good) dielectric grease if you want. I got a set of new plated busbars and nuts from amazon.

    Posted via the PriusChat mobile app.
     
    #7 mr_guy_mann, Mar 11, 2022
  8. Davethewave

    Davethewave Junior Member

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    5.5 hours. Amazing one module....
    So I cleaned the heck out of all connections. Used dielectric grease. Once bus bars installed sprayed unit with metal protector.
    The "bad" module happened to have the most corrosion on the sensor wire.
    It runs like new again.
    Once again thanks for good advice.
     
    #8 Davethewave, Mar 11, 2022
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