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2004 Prius ABS/Brake/(!) lights steady warning beep

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Beachbummm, Feb 5, 2015.

  1. Beachbummm

    Beachbummm Senior Member

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    On a short trip to the store this morning everything was fine on the way back as I pressed the brake pedal( I got a steady warning beeeep that didn't go away and comes on even with the car off as I open the door) and all three warning lights.
    No ABS function when driving and with the car off pedal goes to floor then comes up as the power is turned on. I hear a pump or motor cycling every 10 seconds

    No error code from my hand held scanner

    I did the on board battery check through the MFD and its as follows
    12.2 volt with the car on
    drops to 11.6 with head lights on for 2 mins, turn them off and it goes back to 12.1 (what should the battery voltage be?)
    it seems low too me so I have the battery on an external charger now but need some info as too what may be causing this
    thanks
     
    #1 Beachbummm, Feb 5, 2015
  2. bisco

    bisco cookie crumbler

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    brake accumulator? do you get the 10 second buzz when opening the driver door.
     
    #2 bisco, Feb 5, 2015
  3. Beachbummm

    Beachbummm Senior Member

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    I get a beeeeep when I open the door and the car is off....I guess its about 10 seconds long
     
    #3 Beachbummm, Feb 5, 2015
  4. bisco

    bisco cookie crumbler

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    it's more of a buzzing sound. did you just get the car recently?
     
    #4 bisco, Feb 5, 2015
  5. Beachbummm

    Beachbummm Senior Member

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    no had it for a year,its a warning beep not the hummm of a pump running ..
     
    #5 Beachbummm, Feb 5, 2015
  6. bisco

    bisco cookie crumbler

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    suggest codes be read, and don't drive the car. how many miles on her?
     
    #6 bisco, Feb 5, 2015
  7. Beachbummm

    Beachbummm Senior Member

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    no codes show up on my scanner
    204000 miles
     
    #7 Beachbummm, Feb 5, 2015
  8. valde3

    valde3 Senior Member

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    Basic scanners only show engine codes. If you had warning lights there are codes stored. Read them with hybrid capable scanner. Mini-vci is cheap if you want to do it yourself.
     
    #8 valde3, Feb 5, 2015
  9. nh7o

    nh7o Off grid since 1980

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    Or you can pull blink codes.
    ABS, VSC Lights... Weird!! | PriusChat

    Post here. If you are not hearing the brake booster pump run, then possibly it has failed. Rare but no unheard of at that mileage.
     
    #9 nh7o, Feb 5, 2015
  10. Beachbummm

    Beachbummm Senior Member

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    I hear the pump cycle on and off
     
    #10 Beachbummm, Feb 5, 2015
  11. bisco

    bisco cookie crumbler

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    maybe an ecu? as far as the battery goes, why not check it with a voltmeter in the morning before starting the car? should be 12.5 or better.
     
    #11 bisco, Feb 5, 2015
  12. dolj

    dolj Senior Member

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    You need to use a Prius aware scanner such as Mini VCI.

    This means your 12V battery is essentially a fully discharged.

    For a new 12V (AGM) battery that is fully charged should have a voltage of 13.2V. If it is a few years old and been well maintained, it should be 12.7V or more when fully charged.

    You are correct, as stated above, and that is the correct call to charge up your 12V. When it has charged (for 12-15 hours) let it sit for 3-4 hours and then measure the resting voltage (ACC-Mode). Measure again under load (IG-ON) and report the voltages here. Also, when under load, note the time interval that the voltage continues to drop before remaining steady.

    hope this helps.
     
    #12 dolj, Feb 6, 2015
    Last edited: Feb 6, 2015
  13. Beachbummm

    Beachbummm Senior Member

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    *** UPDATE
    the problem cleared itself as I was driving to the repair shop this morning...I can only assume an electrical connection got wet and it dried out overnight. battery now shows 14.1 on the MFD (to be honest Im a little worried about this happening again next time I hit a puddle..)
    are their electrical connectors for the wheel sensors I can tape up to water proof?
    or is it all built into the harness?
     
    #13 Beachbummm, Feb 6, 2015
  14. dolj

    dolj Senior Member

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    14.1 in READY mode does not tell you a lot about the battery's state of health. Two things you can see from this is a) the charging circuit is working and b) the battery is not fully charged.

    Repeating the ACC and IG-ON tests after charging and reporting here would be more useful.

    What makes you conclude something was wet and dried out rather than your 12V battery is now carrying a more healthy charge to explain the symptoms going away?
     
    #14 dolj, Feb 6, 2015
  15. JazzX4

    JazzX4 Junior Member

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    I have this same issue with the brakes, but the beeping is non stop and it's even deafening. I was told I need to replace the brakes computer or something quite expensive. Is there a way to unplug or stop that beeping at least for the time being?
     
    #15 JazzX4, Aug 13, 2020
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