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C1246, c1252, c1256 codes, brake buzzer, and hard braking

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Bart A Hammontree, Jul 8, 2024.

  1. Bart A Hammontree

    Bart A Hammontree Junior Member

    Joined:
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    Location:
    Knoxville, Tennessee
    Vehicle:
    2005 Prius
    Model:
    N/A
    Hello

    My 2005 Prius suddenly had multiple brake related codes (C1246, C1252, C1256) along with the red brake warning light, brake system buzzer alarm, ABS light, and exclamation mark warning light. Also the brakes seem very hard to engage with the pedal like the power boost has stopped working,and the pedal feels like there is air in the system.

    I had some brake problems a couple years back and replaced the ABS pump with a used unit. Everything has worked fine since then, but it does seem to be loosing brake fluid somewhere. For the last year or so I have to top off the reservoir every 3-4 months with 1/2 pint or so. Before the last ABS pump failure I would hear the pump running and trying to makeup pressure, but this time I do not hear the pump running at all.

    I have access to a laptop with techstream but not sure where to start troubleshooting.

    Any suggestions are greatly appreciated.

    Thanks
     
    #1 Bart A Hammontree, Jul 8, 2024
  2. Tombukt2

    Tombukt2 Senior Member

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    Vehicle:
    2009 Prius
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    Base
    Your reservoir can go up and down about a quarter inch or something like that Just enough for you to notice and people that aren't aware of this add brake fluid thinking that something is happening and then a month later they realize they're overfilled this doesn't really hurt anything unless it's coming out of the rubber top on the reservoir so if you just filling it that quarter of an inch that it's down when it's a quarter of an inch up it's not anywhere near the top lid there's plenty of room in the reservoir just for this reason. So the reservoir moving around a quarter to 3/8 of an inch or something like that is perfectly normal when the pump runs it's pumping up the system and using brake fluid as the medium that's getting pumped so some disappears from the reservoir while the accumulator is pumped up in the system is under pressure. No issue there if you honestly believe you're losing brake fluid then it will continue to go down if that's the case let it go down for a day or so does it ever reach well below the low mark? If so then simply you just need to look at the hydraulic connections for the brakes there's one at each wheel and there's four or five on the actuator You're looking for slimy oily shiny liquid If it's a wheel if it's at a wheel it'll usually be dropping on the back of the rim you shine a flashlight on the back of the rim or through the front spokes and you should see oily residue there's your wheel leak pull that wheel and rim and have a look and see a caliper or a fitting leaking get it fixed straighten it out but I doubt it. Usually it's just the system doing its proper activity.
     
    #2 Tombukt2, Jul 9, 2024
  3. ChapmanF

    ChapmanF Senior Member

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    Half a pint every 3 or 4 months is tough to explain if it isn't going somewhere. The level does look a little lower if you look when there's fluid pumped into the accumulator, and look a little higher if you look when there isn't, but that's just the same fluid bouncing up and down; you can't keep adding half pints to it.
     
    #3 ChapmanF, Jul 9, 2024
  4. Bart A Hammontree

    Bart A Hammontree Junior Member

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    Location:
    Knoxville, Tennessee
    Vehicle:
    2005 Prius
    Model:
    N/A
    Hello and thanks for the feedback.

    I think I am definitely losing fluid somewhere. Depending on how much the car is driven it’s 1/2 a small bottle every few months. The car was 1/2 a bottle low when the symptoms started this week but filling it up hasn’t helped with the symptoms.

    I will get it up on jack stands as soon as possible and see if I can spot any leaks.

    Thanks
     
    #4 Bart A Hammontree, Jul 10, 2024
  5. Bart A Hammontree

    Bart A Hammontree Junior Member

    Joined:
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    Location:
    Knoxville, Tennessee
    Vehicle:
    2005 Prius
    Model:
    N/A
    I had some time this weekend to troubleshoot my braking issues. I started by checking the ABS fuses and relays. I didn’t find any that were bad, but while I had the hood up I heard the ABS pump kick in with the intermittent rattle/buzzing sound. I then noticed that all the warning lights and buzzers had gone away and everything seemed to be back to normal. I took it for a test drive and it worked great for about 10 minutes, then the buzzer and lights came back with no power boost on the pedal. Also I don’t hear any ABS pump noise.

    No idea what to make of this, but planning to see if I can find a copy of the troubleshooting guide from Toyota, and also going to reconnect tech stream to see if I can get more details on the codes.

    Any help would be greatly appreciated.
     
    #5 Bart A Hammontree, Jul 14, 2024
  6. ChapmanF

    ChapmanF Senior Member

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    Vehicle:
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    IV
    #6 ChapmanF, Jul 14, 2024
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