2008 Toyota Prius would not start without jump. No codes.

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by quip1337x, Nov 4, 2025 at 4:33 PM.

  1. quip1337x

    quip1337x New Member

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    This has happened twice now. The car will be completely dead requiring a jump start. The second the cables are attached the prius restarts. Checked the 12 V bat and it said "good, needs charging". OBD2 shows no codes. the car was on the second bar of low gas. i dont think i left any lights on. Checked common fuses on right of box. Im not sure if its a low gas problem because after a jump it ran just fine. even restarted. From what i looked up the common issues are inverter water pump or Dc/Dc converter. but both those would pop a OBD code. Checked the hybrid battey and its above the wattage or voltage.
     
    #1 quip1337x, Nov 4, 2025 at 4:33 PM
  2. PriusCamper

    PriusCamper Senior Member

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    My experience is you need to clean and inspect all the connections around the 12v battery. And yes it's normal when there's no 12v power for the Prius to act weird and try to start up partially once it's 12v power is restored and this is easily fixed by turning the vehicle off then back on again the way you normally do.
     
    #2 PriusCamper, Nov 4, 2025 at 8:32 PM
  3. bisco

    bisco cookie crumbler

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    how old is your 12 volt. 'good, needs charging' may not tell the whole story. did you charge it?
    what did you test it with?
     
    #3 bisco, Nov 4, 2025 at 8:35 PM
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  4. quip1337x

    quip1337x New Member

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    i took it to o'rileys and the tester only said "Good, Needs charging." about a 4 year old battery. No I didnt charge the 12V. i sat in the car with the car powered on for 30 minutes as a comment said to online would help the 12v.
     
    #4 quip1337x, Nov 4, 2025 at 8:44 PM
  5. BiomedO1

    BiomedO1 Senior Member

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    Check battery power at jump point under the hood. You may have a good battery in the trunk, but no power going to the front of the car.
    You still need to perform battery test, to rule that out as the issue.
    You don't have a DC-DC converter issue, otherwise the car wouldn't run - once started. DC-DC converter is same as alternator in a regular car. If it's dead, car wouldn't keep running once you disconnect the jumper cable.
     
    #5 BiomedO1, Nov 4, 2025 at 9:01 PM
  6. quip1337x

    quip1337x New Member

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    Could you explain further how to check or what to look for? is the battery test you speak of the same as the first battery test you spoke of?
    are you talking about the hybrid battery because i checked the voltage or wattage and its above the recommended minimum. Thank you for the Dc/dc info. I'm trying to figure out how much this will cost to fix or if its just better to trade it in.
     
    #6 quip1337x, Nov 4, 2025 at 9:10 PM
  7. quip1337x

    quip1337x New Member

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    I went back to O'rileys and the tester when connected to the front jump terminal was showing 12v. i dont know what that means but man said it was good.
     
    #7 quip1337x, Nov 4, 2025 at 9:56 PM
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