ABS, BRAKES, and Traction Control lights turned on, then off?

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by WatsonW, Jul 30, 2021.

  1. WatsonW

    WatsonW New Member

    Joined:
    Jul 30, 2021
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    Location:
    Greensboro, NC
    Vehicle:
    2012 Prius
    Model:
    II
    Hello! I purchased my 2012 Prius with 96,000 miles this Monday, and when driving home today (sunny, clear weather) I noticed that three lights had turned on on the dash; the ABS, BRAKES, and Traction Control lights. In addition to this, there is a whirring sound that happens every ~10 seconds or so that I believe to be the brake actuator, though this sound had been happening about this frequently since the test drive Monday.. The brakes themselves seem to be working fine, and the regenerative breaking is still operational.

    After a few hours of googling all of the possibilities that it could be, I came back to the car a few hours later only to have a clear dashboard, and no sign of any trouble.

    So far, I have...
    1. Driven around my apartment's parking lot (Brakes work fine, lights didn't come back on)
    2. Tested my 12v Battery via the Vehicle Signal screen (Interesting results here):
      Without the engine running you can see the whirring noise actually making the voltage dip, and with all the lights on, AC on full blast, windows moving, and the whirring happening, I was actually able to get the voltage down to 11.1... Battery needs changing?
      With the engine running the voltage just stays around 14.2, with or without whirring
    3. Tried pulling codes with an OBDII scanner, but either I don't have the right one (likely) or the system doesn't have the codes anymore since the lights turned off.
    Suspected culprits are:
    1. Low 12v Voltage, which seems to be able to throw some weird codes on Priuses
    2. Failing brake booster assembly or brake booster pump assembly, which looks like it might be covered by Toyota via their "ZJB Customer Support Program" if I have the "right" parts that went wrong
    3. Some other failure in the braking system?
    So my questions:
    1. Should I take this car back to the used car dealership? I am still under their 7 day guarantee, so would be able to get my money back/ get a credit towards a different car.
    2. Should I try to get this car fixed by Toyota under the ZJB Customer Support Program? Does this seem to be that issue? Or not, since I'm missing the Red Warning Light and beeping mentioned by the program?
    3. Is there a chance the dealership "pulled a fast one" on me with this car? I bought from a very reputable and decently large dealership so I would be surprised, but is there any chance they knew the brake system was failing before selling the car?
    4. Is this car safe to drive for now? I'm definitely going to get this checked out, but would like to know if it is safe to drive to the dealership/mechanics, or if I should hire someone to tow it.
    Thank you loads for reading this far, and thank you greatly in advance for any advice you have to offer!

    (I have videos of the whirring sound and Vehicle Signal screen, but cannot yet post them as I don't yet meet the requirements.)
     
  2. rjparker

    rjparker Senior Member

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    Vehicle:
    2012 Prius v wagon
    Model:
    Three
    Take it to a Toyota dealership with codes. Don't clear them with a scanner or by disconnecting the 12v. A new brake booster now at Toyota's expense is what you want.

    If you read 11.1v in Ready you have problems. Either with your testing or with the dc to dc converter.

    Ready is the important thing when testing; "running engine" just means the high voltage battery needs charging or you are driving. Most likely you were in the On position, not Ready. In the On state no charging is occurring.

    In either case 11.1v means the 12v battery is low and should be charged, ideally with a battery maintainer like the $28 Battery Tender Jr. But solve the Brake Booster issue first, its $2500 or more if you end up paying for it because you missed the free replacement window at Toyota. But they have to see the codes. Don't clear them.
     
  3. WatsonW

    WatsonW New Member

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    Location:
    Greensboro, NC
    Vehicle:
    2012 Prius
    Model:
    II
    I think I should still be within the window for getting the replacement; the specifications I've found say either August 31st of this year, or 150,000 miles/ 10 years from first date the car was used. Unless we're thinking of different replacements?
    upload_2021-7-30_11-23-43.png
    Either way, you seem sure that the issue with the brakes is related to that faulty booster, could it not be a separate issue? I've just read that it really good be a bunch of different things, but that the Brake Booster issue seems to be a common one.

    Another thing I discovered while driving is that braking hard causes the lights to go off. I'm in the process of getting the codes off and realize this will be the greatest help, but does this help the diagnosis process any?

    When I got the 11.1, it was under decently heavily load (and I now realize that this matters) and only had two bars of charge. Whenever the battery is better charged it hovers around 12.6 at "Ready," and doesn't dip below 12v. Is there still likely a 12v change in my near future?
     
  4. Grit

    Grit Senior Member

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    Location:
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    Vehicle:
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    Model:
    Four
    sounds like carmax, I’d refund it. If I buy a car, it’s has to run without any issues for a very long time.
     
  5. rjparker

    rjparker Senior Member

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    Location:
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    Vehicle:
    2012 Prius v wagon
    Model:
    Three
    It sounds like something is very wrong with the 12v battery or the charging system. You should always have 13v or higher in Ready no matter what. Unless the 12v battery is sucking a huge charge which is far from normal. Most likely the battery is bad but even that is over $200 for a decent replacement.

    Given its very likely you have brake booster problems, I would guess the 12v problem may be resetting the codes. No codes, no free replacement and you only have a month to qualify. Otherwise its on you for $2,500 or more.

    This model has other issues as well, enough where I would advise a prospective buyer to find something else. Since you still have the option for six days, I would return the car and buy a non-hybrid Toyota or Honda in your price range.
     
  6. Kate M

    Kate M Junior Member

    Joined:
    May 18, 2019
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    Location:
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    Vehicle:
    2005 Prius
    Model:
    One
    Hello, did you return the car or repair brake system? If you repaired, did the Whirring/whining sound disappear?
     
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