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Brake Accumulator or ABS Wheel Sensor Issue?

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by 2GenPrius, Dec 13, 2021.

  1. 2GenPrius

    2GenPrius Member

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    Hi everyone!

    I just bought a used 2012 Prius with 152K on it from a well-known European car dealership.

    Went to pick it up and drove it off the lot.

    I noticed that the Brake Accumulator is always pumping every few seconds while the car is on. Today, as I was driving it, the Brake, VSC (Traction Control) and the ABS light turned on. I freaked out and phoned the dealer right away. They said they would take a look tomorrow, but I'm hoping I don't get the "Sold-As-Is"
    spiel. Stopped by an O'Reillys and their limited scan tool detected NO stored codes, even though the lights remained on.

    I was able to make it back home safely, but when I turned around a left curve (rather dramatically because its a deep curve), all the lights then turned OFF. Parked it at home and noticed that they put brand new brake pads on the front.

    I've been reading horror stories about the costs and labor associated with servicing the accumulator and booster, but haven't come across anyone that mentioned hard banking would turn or make the code disappear (or maybe I am just an idiot that can't use the search function correctly). Cousin did some readings online and said it could be a bad ABS Wheel Sensor. I honestly don't know.

    For those that have seen or know about this issue, please let me know.

    Checked the VIN against Toyota's recall website, and it said there is no open recalls/campaigns.

    Thank you for those of you in advance who can help!
     
    #1 2GenPrius, Dec 13, 2021
  2. tankyuong

    tankyuong Senior Member

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    Sounds like accumulator going out
     
    #2 tankyuong, Dec 13, 2021
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  3. JC91006

    JC91006 Senior Member

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    9 year old Prius with 152k miles at a well known dealership? Well they obviously don't care about their reputation
     
    #3 JC91006, Dec 13, 2021
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  4. ChapmanF

    ChapmanF Senior Member

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    With that, you didn't really need to say anything else. If the pump has to cycle "every few seconds" even while the car is just sitting there with nobody applying the brakes, there is a very bad internal leak. For reference, with good brakes, you should be able to finish a moderate-length book in the car without hearing the pump have to cycle.

    Because Gen 3 has split the works up into two boxes, it is good to know which box you need.

    [​IMG]

    In a case like yours, even though it is the pump (lower box) that you are hearing, the internal leak is most commonly in the booster assembly (upper box).

    At three seconds per cycle, though, you should easily be able to check that with a mechanics' stethoscope before you go buying parts. Just touch both boxes with the stethoscope and note which one sounds like Niagara in between those pump-ups.

    Here is a video that rjparker found where a mechanic replaced the booster assembly (upper box) and resolved a problem resembling yours. The customer had bought both boxes, but the mechanic saw what a pain it is to access and replace the lower one, and never bothered, and didn't end up needing it.



    (The mechanic spends a few unnecessary moments discussing an old recall that was actually about the lower box, and didn't apply to that car.)
     
    #4 ChapmanF, Dec 13, 2021
    Last edited: Dec 13, 2021
    jzchen and 2GenPrius like this.
  5. 2GenPrius

    2GenPrius Member

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    Thanks everyone. It seems that Toyota is/was covering the associated parts under a Customer Support Program with a Primary and Secondary Voluntary effort (ZJB Phase 2).

    • The Primary Coverage will be offered until August 31, 2021, regardless of mileage.
    • After the Primary Coverage, the Secondary Coverage is applicable for 10 years from the date of first use or 150,000 miles, whichever occurs first.

    Hope either Toyota or the dealership I bought it at will take care of this. If not, I'm just screwed to pay to get it done.
     
    #5 2GenPrius, Dec 14, 2021
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