Brakes engage while driving (2013 Prius)

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by NachoPatris, Dec 6, 2023.

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  1. NachoPatris

    NachoPatris New Member

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    I am at an impasse and I need ADVICE. My car is being a shithead. I have an exciting issue where it will automatically apply the brakes while I’m driving. The slip warning light comes on and suddenly I’m hard braking. If I turn the car on and off again, the brakes are no longer engaged and I can drive normally again. This doesn’t always happen. Short drives seem to be fine, but anything longer than an hour and it becomes much more likely to happen. If I drive for a couple hours it’s pretty much inevitable. I’ve gone to three mechanics. One was able to recreate the problem, but said he didn’t have Prius-specific knowledge on how to fix it. The two times at the Toyota dealership, they couldn’t figure it out. One time they told me I just have to wait for it to get worse so they can figure out what it is. I just have no idea what to do. I nearly got rear-ended on the highway last month because I came to a full stop from 70mph. I got this car in July. I have 6 months left on warranty. I have 5 years left on the loan. I do not know what to do from here. Any advice, friends?
     
    #1 NachoPatris, Dec 6, 2023
  2. Air_Boss

    Air_Boss Senior Member

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    This appears not to be a Prius v, and trim level is not mentioned, however, does the car have some form of radar interval keeping or braking?
     
    #2 Air_Boss, Dec 7, 2023
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  3. NachoPatris

    NachoPatris New Member

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    No radar and if I chose the wrong forum please redirect me
     
    #3 NachoPatris, Dec 7, 2023
  4. NachoPatris

    NachoPatris New Member

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    I am at an impasse and I need ADVICE. I have an exciting issue where it will automatically apply the brakes while I’m driving. The slip warning light comes on and suddenly I’m hard braking. If I turn the car on and off again, the brakes are no longer engaged and I can drive normally again. This doesn’t always happen. Short drives seem to be fine, but anything longer than an hour and it becomes much more likely to happen. If I drive for a couple hours it’s pretty much inevitable. I’ve gone to three mechanics. One was able to recreate the problem, but said he didn’t have Prius-specific knowledge on how to fix it. The two times at the Toyota dealership, they couldn’t figure it out. One time they told me I just have to wait for it to get worse so they can figure out what it is. I just have no idea what to do. I nearly got rear-ended on the highway last month because I came to a full stop from 70mph. I got this car in July. I have 6 months left on warranty. I have 5 years left on the loan. I do not know what to do from here. Any advice, friends
     
    #4 NachoPatris, Dec 7, 2023
  5. bisco

    bisco cookie crumbler

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    Welcome!
    How many miles?
    What package?
     
    #5 bisco, Dec 7, 2023
  6. rjparker

    rjparker Tu Humilde Sirviente

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    Unless it a Trim 5 AND has the optional pre-collision package (rare) which can apply the brakes, it almost has to be the master cylinder or needs a comprehensive brake bleed using Techstream. On this car the master cylinder is a brake by wire system with abs, brake ecu and more built in. It is known as a brake booster or a brake actuator and does fail but not in this manner. I would wonder if someone installed a used brake booster and failed to get a good one or put in the wrong one. Normally there would be codes and lights.

    Again a pre-collision package is rare; but a brake booster is in all Toyota hybrids.

    If you have LED headlights it is Trim 5


    Pre-collision control button under steering wheel if installed


    Even if its a Trim 5 Pre-collision was still an option.
     
    #6 rjparker, Dec 7, 2023
    Last edited: Dec 7, 2023
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  7. ChapmanF

    ChapmanF Senior Member

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    As the slip warning light comes on, the car clearly thinks it is reacting to something.

    Using a suitable scan tool, please post the contents of the ABS History, which will show the last four times the ABS or slip control activated and what all of the sensor inputs were at those times.
     
    #7 ChapmanF, Dec 7, 2023
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  8. bisco

    bisco cookie crumbler

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    you need to read the trouble codes with a prius appropriate scanner
     
    #8 bisco, Dec 7, 2023
  9. Tideland Prius

    Tideland Prius Moderator of the North
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    *Moved to Gen 3 forum*
     
    #9 Tideland Prius, Dec 7, 2023
  10. bettergolf

    bettergolf Active Member

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    If you have warranty, take it back and tell them to fix it or replace the car if they can't.
     
    #10 bettergolf, Dec 7, 2023
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  11. Tombukt2

    Tombukt2 Senior Member

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    I was going to say scanning should net you some kind of data with the skid control coming on and think something's happening I know if I put a wrong size tire on my car it will activate slip skid control whatever it's called constantly it'll never let me get above 59 miles an hour practically It doesn't really apply the brakes but it doesn't allow you to move forward well but I guess maybe it can apply the brakes or the electric part or something so then I would think something with the skid control ECU with your data logging should tell you.
     
    #11 Tombukt2, Dec 7, 2023
  12. 562 Prius

    562 Prius New Member

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    Did you ever figure this out? Our Prius did the same thing a few times.
     
    #12 562 Prius, Feb 22, 2024
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