Master Warning Light and More

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by PriusII&C, Jul 11, 2025 at 12:17 AM.

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  1. PriusII&C

    PriusII&C Active Member

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    2012 Prius 144k miles. Car has been performing well and no major issues. However it suddenly displaces a few warning lights: check engine, brake, traction control, and the master warning yellow triangle light. Pictures attached. Don't know what is wrong. Hope to get your insight. Screenshot_20250710-205906_Gallery.jpg Screenshot_20250710-205919_Gallery.jpg
     
    #1 PriusII&C, Jul 11, 2025 at 12:17 AM
  2. Grit

    Grit Senior Member

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    Since reading check engine codes wasn’t an option, your local mechanic will be your best option.
     
    #2 Grit, Jul 11, 2025 at 12:46 AM
  3. Brian1954

    Brian1954 Senior Member

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    Did you ever think about using a scanner to reading the trouble codes that the car is trying to tell you about?

    Is this a 2012 Prius OR a 2012 Prius c?
     
    #3 Brian1954, Jul 11, 2025 at 8:55 AM
    Last edited: Jul 11, 2025 at 9:21 AM
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  4. PriusII&C

    PriusII&C Active Member

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    Not sure if we should drive the car, so purchased a scanner online and waiting for its arrival. Will update once getting the codes.

    It is the 2012 Prius.
     
    #4 PriusII&C, Jul 11, 2025 at 9:50 AM
  5. ChapmanF

    ChapmanF Senior Member

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    #5 ChapmanF, Jul 11, 2025 at 9:53 AM
  6. Brian1954

    Brian1954 Senior Member

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    What make and model of scanner did you purchase?
     
    #6 Brian1954, Jul 11, 2025 at 2:07 PM
  7. PriusII&C

    PriusII&C Active Member

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    Just got the scanner Ancel AD310, error code P0A80. It looks like I may have a traction battery problem.

    How far / long can I drive the car with the error code on? What kind of consequence will it have?
     
    #7 PriusII&C, Jul 12, 2025 at 8:31 PM
    Last edited: Jul 12, 2025 at 10:08 PM
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  8. Brian1954

    Brian1954 Senior Member

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    Try to keep everything in one thread rather than multiple treads.

    Copied from one of your other threads:
    Copied from the Grid Charger thread:
    Continuing the discussion in this tread. It would be very valuable information to look at the freeze frame data for the P0A80 code. The Ancel AD310 scanner that you purchased is a very basic scanner. I think it is not able to read freeze frame data for trouble codes. The freeze frame data will pinpoint which battery block is the problem in your battery pack. If you are going to recondition the battery pack yourself, you will need a better scanner to find the bad battery modules.

    I am assuming that your car has been driven back to your home where you are able to work on it.

    Post a screenshot of the Dr Prius app showing the battery data.
     
    #8 Brian1954, Jul 16, 2025 at 1:05 PM
    Last edited: Jul 16, 2025 at 1:25 PM
  9. PriusII&C

    PriusII&C Active Member

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    Here is the screenshot I just took.
    Prius Battery.jpg
     
    #9 PriusII&C, Jul 16, 2025 at 1:59 PM
  10. Brian1954

    Brian1954 Senior Member

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    Thank you for the screenshot. The Delta SOC (state of charge) is showing 11.00%. A healthy battery pack has a Delta SOC of 0.00%. The Delta SOC is the difference in the SOC of the battery blocks. This means the battery blocks are not balanced to each other. In this case, a grid charger should be used to do a 24-hour low current balance of the battery pack. This should bring the Delta SOC back down to 0.00%. A complete reconditioning of the battery pack (charging and discharging cycles) per Prolong's instructions is recommended to regain some of the lost capacity of the battery modules.

    I use the Prolong charger and discharger one time a year to recondition the battery in my 2011 Prius 151k miles. I have done this for the past three years just to keep my battery in good condition. I have been very happy with the results.
     
    #10 Brian1954, Jul 16, 2025 at 2:54 PM
  11. PriusII&C

    PriusII&C Active Member

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    Thank you @Brian1954 for your analysis and advice. I plan to DIY a grid charger, and will let you know the result after completion.
     
    #11 PriusII&C, Jul 16, 2025 at 3:21 PM
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