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2011 Prius going into accessory mode

Discussion in 'Gen 3 Prius Main Forum' started by Lkmckin, Apr 25, 2022.

  1. Lkmckin

    Lkmckin New Member

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    My 2011 Prius, which I have owned since new, has recently not been booting up properly. Instead, it has been going into accessory mode even when the brakes are depressed. Usually I can get it back into normal mode by turning off the power and trying again, 1-4 times so far. Of course I am afraid that the failure will become permanent.
    Scanning for codes with my scanner gives “no codes “. When the car eventually goes into normal mode, I have gotten a “hybrid system overheat” box for a few seconds. Since this problem usually happens after the car has been sitting for >12 hrs, that message seems like a red herring.
    Any ideas about what could be the problem here?
     
    #1 Lkmckin, Apr 25, 2022
  2. JC91006

    JC91006 Senior Member

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    Have you checked the 12v battery?
     
    #2 JC91006, Apr 25, 2022
  3. CR94

    CR94 Senior Member

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    Do the brake lights come on when you press the pedal?
     
    #3 CR94, Apr 25, 2022
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  4. Lkmckin

    Lkmckin New Member

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    Good ideas.

    Brake light does come on when brake pedal is depressed. Of course, the failure is intermittent so that might not be definitive.

    12V battery reads 11.1 V. Seems low to me. I will likely go get a new battery and try that.
     
    #4 Lkmckin, Apr 26, 2022
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  5. Mendel Leisk

    Mendel Leisk Senior Member

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    Yeah very low; how old is it?
     
    #5 Mendel Leisk, Apr 26, 2022
  6. bisco

    bisco cookie crumbler

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    some have reported pressing the go button too soon while applying brake, when in a hurry
     
    #6 bisco, Apr 26, 2022
  7. Lkmckin

    Lkmckin New Member

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    The battery is years old. 4-6, I don't recall. But old enough that replacing it is almost certainly the place to start given the low voltage.

    We've owned the car since it was new. I thought the same about not depressing the brake properly when it first happened to my wife. Then it happened to me, and it took 5 attempts to get it into normal mode after shutting down the accessory mode. Not normal behavior for sure.
     
    #7 Lkmckin, Apr 26, 2022
  8. Grit

    Grit Senior Member

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    There is a button type switch that is behind the brake pedal assembly. As you step and hold the brake down, the button is pressed down and the car will go into ready mode. A few have said the button assembly becomes loose over time and readjusting the button switch back into place resolved the issue.
     
    #8 Grit, Apr 26, 2022
  9. phensolo

    phensolo New Member

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    Had the same issue. Check the battery and check for phantom electrical drain if the battery is less than 5-7 years old.
     
    #9 phensolo, Apr 28, 2022
  10. Lkmckin

    Lkmckin New Member

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    Replaced the 12V battery, and the issue seems to have been corrected.

    Thanks for the advice.
     
    #10 Lkmckin, Apr 29, 2022
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