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Ready light doesn't always come on when starting my 2010 Prius

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Bobbyg1, Sep 4, 2015.

  1. Bobbyg1

    Bobbyg1 New Member

    Joined:
    Sep 4, 2015
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    Location:
    Bethlehem, PA
    Vehicle:
    2010 Prius
    Model:
    IV
    Is anyone experiencing this? This started about 2 months ago. About 10% of the time when I depress the brake and press the Power button, all the dash lights come on except the Ready light (it acts as if I pressed the Power button twice without my foot on the brake). When I depress the brake a second time and press Power button again, the Ready light will still NOT come on. I have to press Power button with foot off the brake to shut off the dash lights (the car is effectively off) and then when I press Power button with foot on brake a second time, the Ready light will come on. I effectively have to try to start the car twice. I also noticed that the interior lights are dimmer when I open the driver's door until it goes through it's normal noisy gyration (something to do with the brakes?). I'm thinking that the 12-volt battery is starting to fail. Does my Gen III 2010 Prius have a diagnostic tool to check the battery?
     
  2. bisco

    bisco cookie crumbler

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    Plug-in Base
    welcome to priuschat! best way to check the 12v health is with a $10. digital volt meter at the jump point under the hood. if it reads 12.5 or better after the car has been off a few hours, it's okay. next, back the car up against a wall and see how hard you have to press the brakes to make the brake lights come on. if it feels to hard, the brake switch behind the pedal can be adjusted. all the best!(y)
     
  3. xliderider

    xliderider Senior Member

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    Three
    The brake sensor switch could be failing as well, not just requiring adjustment.
     
  4. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    Location:
    Greenwood MS USA
    Vehicle:
    2012 Prius v wagon
    Model:
    Three
    Yes, your 12 volt battery seems to be weak,Toyota's TrueStart replacement battery has a 84 month prorated warranty, or any S46B24R sized AGM battery
     
  5. rjparker

    rjparker Tu Humilde Sirviente

    Joined:
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    Location:
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    Vehicle:
    2012 Prius v wagon
    Model:
    Three
    Yes this worked on my 2012 Prius v 3 with Display Audio:

    Realtime 12v Battery Voltage in Off or Running State

    You can easily check out your battery status/charging system by using the MFD Service Menu.

    1 Get your Prius into "Accessory Mode" .
    -- Press the power button without touching the brake pedal.

    2 Put the MFD into "Service Menu" mode (green)
    -- Press and hold the "CAR" button on the MFD while turning the headlights on and off 4 times.

    3 Press the "Function Check / Setting" field on the screen.
    -- "Function Check / Setting menu will appear.

    4 Press the "Vehicle Signal" field.
    -- "Vehicle Signal Check Mode" screen will appear, showing

    Battery 12.3v ---------SPEED 0 Km/h
    IG OFF -----------------TAIL OFF
    PKB ON ----------------ADIM/TCAN BRIGHT
    REV OFF

    The 12v battery voltage will be listed and changes as load changes.

    5 My 2012 v read 12.3 initially. When I turned on the lights it went to 12.4v.

    6 Now get your Prius into "Ready Mode" - step on the brake and press the power button.
    -- The battery voltage should immediately rise to at least 13.8 volts. Mine went to 14.8.

    7 Shutting the car down will reset the system back to normal operation.
     
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