Intermittent issue not starting

Discussion in 'Gen 2 Prius Technical Discussion' started by Marcher, Feb 1, 2023.

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  1. Marcher

    Marcher New Member

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    2008 Prius intermittent issue won't start. No codes showing up on scan tool. Dealer charged over $1100 replacing12v battery, running diagnostic tools, no codes showing. They also ran it for 2 weeks with them driving it daily - no issues. Started every time. Returned to me and next day, same issue, woukdn't start. Friend checked big battery and terminals corroded. Cleaned them and pulled big batter out and checked each cell with voltmeter - all over 7.6v. Put all back together. Drove perfectly for 2 weeks - BIig battery showing as charging well when driving. Then out one day and same issue. Car wouldn't start, has several lights on dash, sometimes red triangle, sometimes not. Car is immobilised as can't get it out of park. Called roadside assistance and they said faulty 12v battery, jump started ok. Bought jump starter pack but when car wouldn't start again, jumping didnt work off starter pack or off another car. 12v battery has 12.7v when tested with voltmeter. I have looked for hours on the internet and other forums but havent found anything that explains my car going one day and not the next over a period of 3 months. Any ideas?
     
    #1 Marcher, Feb 1, 2023
  2. bisco

    bisco cookie crumbler

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    i hate to say it, but it sounds like a loose connection. check the neg to ground at the battery, and the voltage at the jump point under the hood
     
    #2 bisco, Feb 1, 2023
  3. dolj

    dolj Senior Member

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    +1 to bisco's suggestion.

    Check all battery connections at the battery and ensure both the positive and negative terminal clamps are fully seated right to the bottom of the terminal post. If they are not, loosen off the clamp bolt and open up the clamp with a small pry bar or large screwdriver then place right to the bottom of the terminal post and tighten**. Test for a secure connection by giving them a fairly assertive attempt to twist the clamps. They should not move.

    It should also be mote that both the outside of each terminal post and the inside of each clamp should be free of any corrosion and should be clean and shiny.

    ** Use the closed end of a box wrench or a socket to ensure you do not lever the clamp upward accidentally.
     
    #3 dolj, Feb 1, 2023
  4. TMR-JWAP

    TMR-JWAP Senior Member

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    When you have this happen, does your fuel gauge change to one blinking dot? Do you lose the auto-up-down function of the driver window (is the word AUTO on the driver side window button blinking? sometimes it's hard to tell outside of night time) does the radio lose it's preset stations?
     
    #4 TMR-JWAP, Feb 1, 2023
  5. Marcher

    Marcher New Member

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    Thanks all, all battery terminals checked, good connections. All electrical functions work, radio, lights, windows. No one blinking dot for fuel guage. Tried everything today nothing works - forgot to mention gear lights flashing. All forums say check fuses - have checked all under the bonnet and under steering wheel. Also tried to see what issues on function screen but all were ok on first screen but then touch screen doesn't work to move to next screen. Tried scan tool - worked last week, now saying can't connect. Tried over ride by connecting scan tool 5 and 4 - again worked a couple of weeks ago but no change this time. Out of ideas and ready to sell for scrap!!!! Any suggestions welcome but we have tried all the normal things. Will not start, can't move it!
     
    #5 Marcher, Feb 4, 2023
  6. Marcher

    Marcher New Member

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    Yep all checked and ok.

    thx but none of the above
     
    #6 Marcher, Feb 4, 2023
    Last edited by a moderator: Feb 5, 2023
  7. bisco

    bisco cookie crumbler

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    what does the voltage measure at the jump point under the hood with the car off
     
    #7 bisco, Feb 4, 2023
    edthefox5 likes this.
  8. TMR-JWAP

    TMR-JWAP Senior Member

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    Swap out the power source ecu
     
    #8 TMR-JWAP, Feb 4, 2023
  9. Marcher

    Marcher New Member

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    12.7.

    Sorry I am a newbie - do you mean buy a new ECU or is this a fuse to swap out???
     
    #9 Marcher, Feb 5, 2023
    Last edited by a moderator: Feb 5, 2023
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  10. edthefox5

    edthefox5 Senior Member

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    Ok sure sounds like the 12 volts.

    Lets exonerate it:

    Get your DC voltmeter. With CAR OFF check the voltage at the front jump point. Write that down.

    With car STILL OFF turn on the headlights in high beam. Let them run for 5 minutes. After 5 mins turn them off. Wait one minute and
    measure the voltage at the front jump point. Whats it read?

    Lets see how the battery handles this pretty benign load. I bet and hope your battery tanks under this test. Some bad battery's will die so be prepared to jump the battery if it fails. A healthy battery has no problem with this test and should only drop about a half a volt.
     
    #10 edthefox5, Feb 5, 2023
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