My 12V Battery is dying

Discussion in 'Gen 5 Prius Care, Maintenance and Troubleshooting' started by priusasa, Dec 13, 2025.

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  1. VelvetFoot

    VelvetFoot Active Member

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    I don't know....
    upload_2026-1-20_18-37-34.png
     
    #81 VelvetFoot, Jan 20, 2026
  2. VelvetFoot

    VelvetFoot Active Member

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    I wonder if some future decision to compensate owners who paid to have a defective part/design fixed would be in favor of the dealer fix, or the do-it-yourself/eBay fix? Future compensation is probably only wishful thinking.

    @soft_r did a nice video on taking the console apart.

    I wonder what the Mass criteria is for passing state inspection? I'm under the impression it was only smog in NY, but I could be wrong. You can get a message for any tricky tacky thing. I would think it would just have to pass the engine readiness test when they plug in their obdc reader.
     
    #82 VelvetFoot, Jan 20, 2026
  3. BiomedO1

    BiomedO1 Senior Member

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    It depends on the shop, state rules, and regulations. Most shops around here will automatically fail you, if the check engine lamp is ON. They won't even pull it into the shop, but they won't charge you either. If you insist, they'll charge you then fail you - though out here the issue needs to be smog related. How would you know, unless you've got your own scanner and know what codes was thrown and if they are smog related? Whomever signs-off on that certification is liable - they don't want to lose their license and livelihood over stupid stuff, so safer to simply fail you.
     
    #83 BiomedO1, Jan 20, 2026
  4. priusasa

    priusasa Member

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    If they give me 459 dollar when I fix myself, I could do it. :D

    The mechanic guy told me that if there is check engine light and a code, it will fail. I told him that I dont have check engine light. Also, when I use my cheap obd2 scanner, there is no code either. But when I use techstream, there are codes. It's gamble. if I go there and make him check and see the codes, it will fail.

    Thats the issue. I dont have check engine light. I have warnings. BUT I also have codes when I plug in the techstream.

    Maybe I will go there and beg him to check if it would fail when he does the inspection.
     
    #84 priusasa, Jan 20, 2026
  5. VelvetFoot

    VelvetFoot Active Member

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    I think if you don't have a check engine light, and the engine says it's 'ready', with zero engine dtcs when he plugs his machine in, there might be a chance that you're okay. After all, how many ECU's are there in the car? Should the car fail state inspection because there's a code for a faulty window operator? But that would be logical, and who knows what the state's view is.
     
    #85 VelvetFoot, Jan 20, 2026
    priusasa likes this.
  6. priusasa

    priusasa Member

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    So the Toyota dealer ghosted me, I am on my own. I will try to fix it when the weather is warm enough. I will update here. Probably I will take that part apart and check the capasitors inside. If I can locate the bad capasitor, I will just replace that capasitor. So I dont need to pay 300 (ebay)-1200 (Toyota) dollar part
     
    #86 priusasa, Jan 29, 2026 at 2:07 PM
    VelvetFoot and bisco like this.
  7. Mendel Leisk

    Mendel Leisk MMX GEN III

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    Maybe get a decent prosumer level battery tester, see where yours is at. They test voltage AND Cold Cranking Amps, and usually will give a verdict on it's condition. Here's an example, an updated version of what I'm using.

    Also, test for how much amperage is constantly being applied to the battery, when the car's completely off. It should be around 20 milliamperes, 40 max. A video on that process:

     
    #87 Mendel Leisk, Jan 29, 2026 at 2:38 PM
  8. VelvetFoot

    VelvetFoot Active Member

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    That could be awesome. I wonder if you can drive around with it removed?
     
    #88 VelvetFoot, Jan 29, 2026 at 3:31 PM
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