Car moves with brake ON and put then into drive

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by silentak1, Feb 24, 2012.

  1. silentak1

    silentak1 Since 2005

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    I've had this issue ever since I bought the car in May 2010 and the dealer wants me to leave the car for a few days without a loaner...so I've been post-poning bringing it back (oh and now i'm past the 36k mark...at 40k already). Worse of all, the problem is so random that I feel that after those few days, they won't be able to replicate and just return it back to me without a fix. I think those of us who have tried warranty claims experience this often.

    This problem happens at random, in all types of weather conditions, doesn't matter if I drove a mile or a hundred miles. Original brakes, all service to date done at the dealership (mostly oil changes). The ABS recall was performed before I purchased the car.

    I park my car with the emergency brake ON and turn off the car. I come back a while later and start the car the normal way take the emergency brake OFF, press on the regular brake and HOLD the pedal, turn on the car, shift into D or R and then....the car will sometimes start moving unless I let go off the brake and press it again! (Usually in a semi-panicked reaction making me look like an idiot in a parking lot). Almost as if I wasn't pressing on the brake. :eek:

    The only thing that I have always noticed is that when the car starts moving, if I try to press HARDER on the brake it actually doesn't do anything. In fact, it's HARD to press further down (almost as if I had it floored but it's not) so I have to let go and press again.


    Anyone else experience this? I would say this happens about once a month or so and I'm almost getting used to it, but obviously this isn't normal. Maybe there's something off about the drive-by-wire system. :noidea:
     
  2. bisco

    bisco cookie crumbler

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    wow, can this have anything to do with the hill assist?
     
  3. silentak1

    silentak1 Since 2005

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    Good point, I know how to engage hill assist and I assure you that I don't press on the brake that hard when I start the car, you know, just soft to medium pressure 25-30% of the way so I can engage a gear. And the hill assist link doesn't come on when this problem happens.
     
  4. bisco

    bisco cookie crumbler

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    it is very odd, i wonder if it's an adjustment in the pedal or tranny interlock? sorry, i'm just guessing here.
     
  5. qbee42

    qbee42 My other car is a boat

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    This can't have anything to do with the transmission or parking pawl. Since the service brakes are applied, no normal amount of creep could possibly make the Prius move. Assuming the OP's description is correct, this means that the service brakes are not applying hydraulic pressure to the brake cylinders. Pumping the brakes restores pressure. This sounds like a brake ECU issue, or something wrong with the brake master unit, whatever it is called.

    Tom
     
  6. spiderman

    spiderman wretched

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    Are there any warning lights/sounds?
     
  7. fuzzy1

    fuzzy1 Senior Member

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    How hard are you pressing the pedal? At least 112 pounds?

    This pedal force (actually 500 newtons) is a magic number for some federal regulations. It should override all the drive-by-wire stuff, bypassing any electronics faults and applying direct mechanical / hydraulic force to the brakes. It should even bypass any single mechanical / hydraulic brake circuit failure by putting sufficient holding force on the other brake circuit. If that much pedal force won't hold the car still, and the shop can't find anything wrong or the car shows no warning indicators, then it is time to file a defect report with NHTSA.

    While the great majority of alleged Toyota brake failures are operator error, that doesn't mean absolutely all of them are so. I'd hate to see a real but rare car problem ignored under the flood of driver errors.
     
  8. Rebound

    Rebound Senior Member

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    Because you reported this to the dealer during the warranty period, they will most likely repair this under warranty. It sounds to me like something you should take care of.
     
  9. wick1ert

    wick1ert Senior Member

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    I wonder if any of the ECUs put a stored code that isn't causing any warning lights to go on. If you were on the opposite coast, I'd try to hook it up with the cable to TechStream and see if there were any stored codes.

    Has the dealer even hooked it up to see if there's any stored codes? How frequently would you say this happens?
     
  10. yeldogt

    yeldogt Active Member

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    Have the brakes on this ever been serviced?

    I don't know what was done at the recall --- but at the very least this car should have a complete fluid change ... not just a bleed. I had a car that must have had some air in the ABS unit that did what you describe -- mostly in the morning when the engine would be running faster and the operator would use normal pedal force ....... it was totally random.
     
  11. silentak1

    silentak1 Since 2005

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    You just reminded me or something. In a period of ownership since May 2010, I did notice that my brake fluid reservoir was at the low mark (strangely). I added some more DOT 3 or DOT 4 to the full line, whichever one the cap suggested. There are no leaks from the bleeder nipples at each caliper either, is someone stealing my brake fluid? :p No really... no leaks and yet it's consuming fluids. No funny sounds from the brake master cylinder, I know what an air leak sounds like and don't hear that here.

    Nothing, standard start-up.

    Not sure how many lbs i'm applying, but the normal pressure if that's any help! This is my second Prius... I have about 120,000 miles driving both my old and new prius and I don't think it's me because even with the same pressure, it usually doesn't happen. Here's the kicker, even if i apply MORE brake pressure while the car is moving (while already holding the brake), the brakes don't grab at all...as if i wasn't pressing. It's only when I release and press again that the car will stop (rather abruptly if i'm semi-panicked; this drive by wire is sensitive stuff).

    Did not know that, thanks. Hopefully they logged my complaint, though I'm doubting... the service advisor didn't look too excited to take on a warranty-issue.

    Happens once a month, sometimes more..maybe twice, and sometimes none. Totally random. Dealer never hooked it up to pull a code, they want the car for a few days. I live in LA and without a loaner I can't get around and yes... I guess I'm being a little cheap and don't want to rent a car for $40/day after taxes... not very logical if you think it's safety related, I know.

    Besides the ABS recall that was done prior the purchase, I have it regularly serviced for the oil change + brake adjustments (though I think it's only for the rear emergency brake). I do have a brake pressure bleeder tool, perhaps this is the first step... it's due for one anyway. Thanks for the reminder and tip!
     
  12. stevemcelroy

    stevemcelroy Active Member

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    OP - These sorts of intermittent problems can be a bear to deal with for both you and the dealer. The issue for them is that without being able to pull a code or reproduce the issue they are at a loss. Before mechanics used to have to actually diagnose issues, these days that is a lost art and most just read codes and fix what the computer says is broken.

    Hopefully this was documented at the dealer prior to your warranty running out - if so it should be in Toyota's system - if so perhaps another dealer would be more accommodating with a loaner.
     
  13. wick1ert

    wick1ert Senior Member

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    You could actually get a car cheaper than that if you priceline it. The competition in your area should allow it to be pretty good. I had a full size rental on Oahu for roughly that, and prices are higher on the islands.
     
  14. silentak1

    silentak1 Since 2005

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    Good point, note taken, thank you.

    I forgot about priceline! Thanks. Now I gotta call the dealership and see if they documented it.
     
  15. priusguam

    priusguam Junior Member

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    My 2004 does this. I step on the brake, shift in to D or R and then it moves a few feet. Scary when your parked at a marina or the kids are around the car. Was there ever any resolution to this issue. BTW, my scan guage shows no codes. Also, my electronic brakes recently failed with the VSC/ABS/Brake light on, but this issue predates that and is still happening. so now im just using mechanical brakes and it still happens. kinda dangerous. wish someone could shed some light onto this.
     
  16. edthefox5

    edthefox5 Senior Member

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    What does this mean? How do you chose between electronic brakes and mechanical brakes?
     
  17. Han

    Han New Member

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    I had a very similar experience recently in my 2008 Prius that was fixed by changing the auxillary battery ~$340 at the dealer with Toyota battery, $150 if you do it yourself with 3rd party battery. The car would turn on with the brake depressed, but the instrument panel would stay alit. Shifting to reverse/drive the car would start moving EVEN WITH THE BRAKE STILL DOWN! This was very scary in parking lots and on hills.

    The workaround for me was to release the brake after starting the car, and usually the instrument panel lights would go off and it would go to ready status.

    I think what must have happened was that there must have been a low voltage on the Aux battery. Releasing the brake must have allowed the engine to run, normalizing voltage, and the rest of everything works once voltage is normal.

     
  18. bisco

    bisco cookie crumbler

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    the 12v does some odd things, but many newbies fail to understand.
     
  19. FrankB

    FrankB Member

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    My 2010 does exactly this, sometimes starts moving with brake depressed after power on, the only way to correct it is to let off and reapply. It will be interesting to see if it stops happening after I eventually replace the original 12V, although I've measured the 12V a few times and it's still reasonable.
     
  20. Han

    Han New Member

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    If I were the only one driving the car, I might not have got it fixed since I learned the workaround. But my wife drives the car too and I worried that she would forget and potentially hit someone in a crowded parking lot.
     
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