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Weird Prii '10 startup issue: sometime not in ready mode and a quick fix I found

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by cb_jimmy, May 15, 2016.

  1. cb_jimmy

    cb_jimmy Junior Member

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    My 2010 prii sometime has this weird startup issue. Occasionally, the car will not get into ready mode. Power and accessories are on but it won't move. Normally, I would try depressing the brake pedal and pushing the Start button (usually took me less than half a minute) until the car turns itself off. It would be back to normal functionality the second time it startups. Recently, I found this alternative quick fix:

    When car refuses to get READY,
    -Open the driver door
    -Depress the brake pedal
    -Push the START

    The READY light would be on and the car is set to go.

    This issue doesn't bother me that much since it only happens rarely. However, it's good to know if anyone has experienced this. What is the cause? a software glitch?

    Another thing I notice, if I use the normal method to restart the car, the battery bars are sometimes falsely reported a lot more charge (full bars) than before the car was turned off. It would then quickly drained to the actual charge.
     
    #1 cb_jimmy, May 15, 2016
  2. JC91006

    JC91006 Senior Member

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    Have you checked the health of the 12v battery?

    SM-N900P ?
     
    #2 JC91006, May 16, 2016
  3. cb_jimmy

    cb_jimmy Junior Member

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    Hmm.. I don't have a voltmeter. Guess I'll bring her to a battery dealer.

    So the 12v battery need replacing if the volt reading falls below 12v?
     
    #3 cb_jimmy, May 16, 2016
  4. dorunron

    dorunron Senior Member

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    Is this the same 2010 that you posted the carfax on? Buying a used Prius 2010 with open recalls | PriusChat

    Prius is well known to have flaky electrical problems when the 12 volt battery gets weak. Buy a cheap volt meter and check it yourself. Check it with a load and without. Post what readings you see.

    Here is a chart for non loaded 12 volt battery for your reference. Your battery is a "AGM" type battery, so refer to the first column. It would not surprise me one bit to find your battery needs replacement. Chances are it is the original battery and therefore would be at least five to six years old.

    Battery SOC Chart.jpg
     
    #4 dorunron, May 16, 2016
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  5. cb_jimmy

    cb_jimmy Junior Member

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    Thank! I'll get me a cheap voltmeter. Should I let the car sit for a night before doing the reading?
    Also, please elaborate a bit about the loaded and non loaded part.

    And no, this is not the Prius I posted in that thread. The one I picked doesn't have outstanding recalls and I think I got quite a good deal for it.
     
    #5 cb_jimmy, May 16, 2016
    Last edited: May 16, 2016
  6. RRxing

    RRxing Senior Member

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    You could also check the brake switch behind the pedal.
     
    #6 RRxing, May 16, 2016
  7. David Beale

    David Beale Senior Member

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    Leave car overnight, check voltage before turning the car on. Unfortunately with a Prius this can't be done without putting some load on the battery (when you open the hatch some lights turn on, like the ones on the bottom inside of the doors). But it's better than nothing.
    For a larger "load check" turn on the headlamps without turning on the car and see what the voltage drops to. It should stay above about 11.5V at the battery. If it gets to 10V or less you have a dead cell.

    The brake lamp switch is also a good thing to check. Park so the tail lamps can be seen in a window. Press the brake pedal lightly, and the brake lamps should come on. If it requires a hard press it's out of adjustment. This can cause trouble getting to "ready" as to get to "ready" the brake switch must be actuated. If it isn't you go to "accessory" then "ign on", neither of which will allow you to actually drive away. Press again and it will go to "off". It's in the owners manual.
     
    #7 David Beale, May 16, 2016
  8. bisco

    bisco cookie crumbler

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    pop the hood in the evening, so you can check the voltage at the jump point in the morning, without opening any doors. you like to see at least 12.4 although some will say less is okay. load test by turning on headlamps and watch voltage drop.
     
    #8 bisco, May 16, 2016
  9. cb_jimmy

    cb_jimmy Junior Member

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    Ok, I bought a multimeter and did the reading this morning. I'm not sure if I'm doing this right. With the dial setting as shown in the attached pic, the meter show 10 on the "&ACV" row during non loaded condition and 9 when I turned on headlight and beam.

    I suppose this is the cause of the startup issue? so the battery need to be retired? The car starts fine most of the time.
     

    Attached Files:

    #9 cb_jimmy, May 17, 2016
  10. Former Member 68813

    Former Member 68813 Senior Member

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    LOL, lost art of reading analog gauges. with the selected range at 50 you read the scale that goes to 50. if it was really 10V, you need a new battery.
     
    #10 Former Member 68813, May 17, 2016
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  11. CR94

    CR94 Senior Member

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    You need "DCV."
     
    #11 CR94, May 17, 2016
  12. cb_jimmy

    cb_jimmy Junior Member

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    I did set the dial to measure DCV. I was just trying to point out the reading location on the gauge.
     
    #12 cb_jimmy, May 17, 2016
  13. dorunron

    dorunron Senior Member

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    If you are reading the meter correctly, then chances are the battery is indeed bad. A digital volt meter is preferred over a "analog" type which you now have.

    I would suggest changing it. Be aware that the battery is a AGM type battery AND that it has "JIS" post's on it.

    In the future, for better accuracy it is suggested that you use a "digital" meter rather than a analog meter. [​IMG]

    Be aware that is possible you may be having issues with the brake light switch also. You need to confirm that the brake lights are coming on "when" you have the problem of the Prius not entering "Ready" mode. If you can confirm that the brake lights are working "ALL the time", then it is suggested to change the 12 volt.
     
    #13 dorunron, May 18, 2016
    Last edited: May 18, 2016
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  14. RRxing

    RRxing Senior Member

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    I'm still thinking it's a brake switch issue.
     
    #14 RRxing, May 18, 2016
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