2007 Prius: Red Triangle + ABS + Engine Check lights :(

Discussion in 'Gen 2 Prius Main Forum' started by Lindsay Mathieson, Nov 22, 2025 at 6:45 AM.

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  1. Lindsay Mathieson

    Lindsay Mathieson Junior Member

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    While driving - close to home fortunately, made it back.

    Have run Toyota Techstream to pull the codes, got the following:

    Hybrid Control:
    • P0A08
    • P3102
    • B2799
    ABS/VSC/TRC
    • C1241
    Air Conditioner :)
    • B1421
    • B1476
    Gateway:
    • B1210
    Quite the list :(

    From my somewhat naive searching, I'm wondering if its the 12 volt battery that's the problem? Is it worthwhile just replacing it as a start before panicking? Same battery from when I purchased the car in 2023

    175k KM on the clock.
     
    #1 Lindsay Mathieson, Nov 22, 2025 at 6:45 AM
  2. Brian1954

    Brian1954 Senior Member

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    If you have a volt meter, use it to measure the 12v battery. Check at the battery terminals and at the jump point under the hood with the car off. Also, check when the car is Ready (on).
     
    #2 Brian1954, Nov 22, 2025 at 9:11 AM
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  3. priumium

    priumium Member

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    All questions should by default be answered with:

    As a person who do not wish to pay for fault codes (since posting here) to any mechanic without any knowledge of the actual issue; get a Bluetooth 4 OBD2 dongle, such as vlink or similar, read the codes from your phone.

    Note to all; This tip may be outside the scope of what Toyota recommends…
     
    #3 priumium, Nov 22, 2025 at 9:40 AM
  4. Hayslayer

    Hayslayer Active Member

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    OP wrote:
    Have run Toyota Techstream to pull the codes, got the following.

    That is just slightly better than any phone app you're going to find............
     
    #4 Hayslayer, Nov 22, 2025 at 10:04 AM
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  5. highmilesgarage

    highmilesgarage Active Member

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    lol, why would you use a phone app when you have techstream.. sometimes you have to think before posting..

    P3102 is hinting a weak 12v battery and did you check your inverter coolant pump?
     
    #5 highmilesgarage, Nov 22, 2025 at 10:12 AM
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  6. Hayslayer

    Hayslayer Active Member

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    sometimes you have to think before posting..

    very good advice, I'm just not sure how that applies to my post
     
    #6 Hayslayer, Nov 22, 2025 at 10:18 AM
  7. Lindsay Mathieson

    Lindsay Mathieson Junior Member

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    Didn't think to check the Inverter Coolant pump, I'll check in the morning. Probably just replace the 12v battery as well - any decent battery will do?

    Thanks!
     
    #7 Lindsay Mathieson, Nov 22, 2025 at 10:56 AM
  8. Brian1954

    Brian1954 Senior Member

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    Do you own a volt meter??? See post #2.

    You could have a bad inverter assembly or a blown fuse. If so, buying a new 12v battery would be a waste of money.
     
    #8 Brian1954, Nov 22, 2025 at 2:34 PM
  9. Lindsay Mathieson

    Lindsay Mathieson Junior Member

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    I activated diagnostic mode, went into Signal Check Mode Section, it shows the battery sitting at 11.0v - thats pretty low isn't it?
     
    #9 Lindsay Mathieson, Nov 22, 2025 at 7:42 PM
    Last edited: Nov 22, 2025 at 7:53 PM
  10. Brian1954

    Brian1954 Senior Member

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    Yes, 11.0v is low. What voltage do you see when the car is Ready (on)?

    Do you own a 12v battery charger?
     
    #10 Brian1954, Nov 22, 2025 at 7:50 PM
  11. Lindsay Mathieson

    Lindsay Mathieson Junior Member

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    I retested with the engine running - 14v

    Turned the engine off and it dropped to 11.8v

    I do typically only use the car a couple of time a week for short trips - just not getting a chance to charge?

    Dashboard warnings have gone except for the red triangle. Should I just clear the codes and take it for a cruise to charge?

    Don't have a battery charger but can probably borrow one, but the battery looks tricky to remove ...

    Thanks!
     
    #11 Lindsay Mathieson, Nov 22, 2025 at 7:54 PM
  12. Brian1954

    Brian1954 Senior Member

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    14v in Ready is good. That means the DC/DC converter inside the inverter assembly is working properly.

    Do not clear any codes yet. Can you use the scanner again to read the trouble codes again?

    You do not need to remove the 12v battery to charge it. Just hook up the charge with the battery in the car. If you can afford to buy a 2 to 5 amp smart charge, that is what I recommend. Connect the charger to the battery for 9 to 24 hours (depending on the charger size) to get a full charge. I use a NOCO Genius 2 amp charger for my Prius.
     
    #12 Brian1954, Nov 22, 2025 at 8:04 PM
    Last edited: Nov 22, 2025 at 8:16 PM
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  13. Lindsay Mathieson

    Lindsay Mathieson Junior Member

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    Will do

    Cool! can afford. Running an extension to the carport could be tricky though....
     
    #13 Lindsay Mathieson, Nov 22, 2025 at 8:10 PM
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  14. Brian1954

    Brian1954 Senior Member

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    I edited my post #12 a little. Please look at it again.
     
    #14 Brian1954, Nov 22, 2025 at 8:12 PM
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  15. Lindsay Mathieson

    Lindsay Mathieson Junior Member

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    #15 Lindsay Mathieson, Nov 22, 2025 at 8:57 PM
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  16. Lindsay Mathieson

    Lindsay Mathieson Junior Member

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    Less codes now:

    Hybrid Control
    • P0A08
    ABS/VSC/TRC
    • C1241
    AirCon:
    • B1421
     
    #16 Lindsay Mathieson, Nov 22, 2025 at 9:50 PM
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  17. Brian1954

    Brian1954 Senior Member

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    The P0A08 seems to be the code to be concerned about. The short description of that code is DC/DC Converter Status Circuit. I do not think that this code is caused by the low 12v battery. The C1241 code is probably caused by the low 12v battery.

    Hook up the battery charge to the terminals of the 12v battery and let it fully charge the battery for 20 to 24 hours if possible. If you can not let it charge for that long, no problem. Just connect the charger again when you can for the remainder of the time.

    Edit: Read the directions for the NOCO charger. If you have the Prius standard AGM battery in your car, you should set the charger to the AGM charging setting.
     
    #17 Brian1954, Nov 22, 2025 at 10:09 PM
    Last edited: Nov 22, 2025 at 10:17 PM
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  18. Lindsay Mathieson

    Lindsay Mathieson Junior Member

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    Will do, thanks for all the help.
     
    #18 Lindsay Mathieson, Nov 22, 2025 at 10:26 PM
  19. Lindsay Mathieson

    Lindsay Mathieson Junior Member

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    Ok, the battery is a Spill Resistant sealed unit, so I'm presuming AGM.

    Hooked up the charger to the under the hood terminals and set it to AGM charging - starting off a lowest charge state I believe.

    Waiting to see if anything bursts into flames :)

    Prius - Charge Points.jpg


    Noco Settings.jpg
     
    #19 Lindsay Mathieson, Nov 23, 2025 at 12:53 AM
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  20. Lindsay Mathieson

    Lindsay Mathieson Junior Member

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    Huh - fully charged (green) already after just 4 hours - should I leave it on for 24 hours anyway?
     
    #20 Lindsay Mathieson, Nov 23, 2025 at 4:32 AM
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