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A new brake issue after the firmware update

Discussion in 'Gen 3 Prius Technical Discussion' started by xvs, Mar 1, 2010.

  1. jdcollins5

    jdcollins5 Senior Member

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    From what I understand, Hill Assist is available on all cars. I know I have it on my III.

    If you will depress your brakes a little harder than normal, a yellow icon will appear in the left side of your display. If you let off the brakes, they will hold for 2 seconds before releasing, giving you time to press the accelerator and start moving on a hill.
     
  2. austingreen

    austingreen Senior Member

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    Hill Assist is on all the 2010 prii. It holds the car from rolling back for a couple of seconds when starting out on a hill. Some other users have confused this with a brake problem, but its a good feature. That doesn't apply to this case though according to the OP.
     
  3. Susan4ET

    Susan4ET Member

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    Very interesting. I've got to find a hill and test this out. I wonder how it works parking on a hill. I like to turn the curb wheel out and let the car drift back a little so the tire just touches the curb before I put the car in 'P' and apply the parking brake. I wonder if the feature will let the car drift back any?
     
  4. xvs

    xvs Member

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    I know the position. It was fully up, not bottomed out.

    I tried to duplicate this several times and couldn't. You can shift to any gear without holding the brake pedal down if you have emergency brake engaged, and that is what I did, but when I've tried to replicate it, the normal brake can still be depressed. In this case, it couldn't.
     
  5. qbee42

    qbee42 My other car is a boat

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    Yes, that will work. You have to manually engage hill assist. If you don't engage it, your Prius will roll back just fine.

    Tom
     
  6. Susan4ET

    Susan4ET Member

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    If I understand the manual correctly... I park, position the wheels, drift back to touch the curb, _then_ press down on the brake further until the slip light flashes and I get a beep. At that point I can take my foot off the brake and have 2 seconds to apply both the parking brake and 'P' before the brake will release automatically. If I want to reposition the car for any reason and don't want to wait the two seconds I can counter the 'hill assist' by pressing down on the brake and release to move the car.

    I guess I'm glad there is no easy way to duplicate the problem but wish xvs could come to some understanding about what happened? Are some/all of these accelerator and brake and cruise control incident 'glitches' un-duplicatable 'bugs/oversights' in the ECS hardware/firmware design?
     
  7. PaJa

    PaJa Senior member

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    Back to OP. The important thing is if he heard the brake pressure pump when he opened driver's door. If not, there was not enough pressure in the system and brakes rely on hydraulic function without assistance. AFAIK the construction of P2010 brakes there could not be link with the "recall" software. This flash has nothing to do with this kind of operation. Brake pedal acts as a input sensor for the braking system combining hydraulic and electric signals.
     
  8. xvs

    xvs Member

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    I heard nothing unusual. I never hear anything like a pump that I notice.

    I don't think it was a pressure issue, because there was ZERO movement at all when I tried to press on the pedal, and when I powered it off, I could instantly press the pedal down, re-start the car, and it then worked as usual.
     
  9. Susan4ET

    Susan4ET Member

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    The problem I'm having at this point is that I don't think there is any situation where the brake pedal would ever not be able to move or be pumped as you describe. Hydraulics just doesn't work that way.

    I just sat in my car with it turned off and tried to bleed off the brake assist pressure to see what the brakes feel like with no assist. I couldn't do it. The electric pump comes on restoring the pressure.

    Is there any way to do this safely to experience what the brakes would feel like if the assist pressure was depleated? Braking would be a lot harder then you normally would ever experience driving the car and this might be what you experienced when you pressed harder then normal thinking nothing was happening?
     
  10. MicroMan

    MicroMan New Member

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    For a long time, but not over 50 years: 2010 - 50 = 1960. 1960 pre-dates the first microprocessor (Intel 4004, 1971), and even the first minicomputer (DEC PDP-5, 1963). The smallest production processor in 1960 was the IBM 1401, which was five feet high, three feet wide and weighed 1 ton. Rather hard to embed under the hood of a car ;)

    The first recorded research effort to use a microprocessor in a car was by GM in 1973. The first production automotive microprocessor ECU was a single-function controller used for electronic spark timing in the 1977 General Motors Oldsmobile Toronado.
     
  11. xvs

    xvs Member

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    I hope you are not calling me a liar.

    Are we certain the brake pedal in the Prius is hydraulic? I was under the impression that it was electronic, as is the accelerator and the steering.
     
  12. JimN

    JimN Let the games begin!

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    I keep a camera in the car so I can document strange occurances to counter the "can't replicate the problem" answer at the dealer. Report the situation to Toyota (although I don't believe contacting Customer Service will get you anywhere) and to the NHTSA. Toyoda & their commercials may say they care but talk is cheap & I personally haven't seen any action.
     
  13. rumpledoll

    rumpledoll Member

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    It is hydraulic. See Mike Dimmick's post here. The diagram is instructive on how complex the Prius's brakes are.

    In normal use the hydraulics from the brake pedal goes to a stroke simulator to give the proper feedback to the driver and the brakes are actuated, hydraulically and regeneratively under ECU control. If the ECU control fails for any reason, the brakes have a fail safe in which they work like regular brakes (the stroke simulator is bypassed) with the brake pedal pressure used to actuate the brake pistons in each wheel.

    I've never experienced this fail safe mode, but in a regular car when the brake vacuum boast is exhausted the pedal can feel like it's not moving and one has to really press down hard to get the car to brake. The Prius in a fail safe mode may not have the brake accumulator providing boost in some failure modes and thus the brake pedal may feel like it's not moving. Perhaps this is what you felt?

    Rumple

     
  14. hitechboy

    hitechboy New Member

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    I think you just experienced the brake grabbing problem. Its was well documented on this forum. The brake pedal became very hard to depress and the brake actually grabbed the discs solid.
     
  15. Susan4ET

    Susan4ET Member

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    Heavens no. I don't doubt your experience at all. I'm just trying to create a reason/explanation that won't one day come down to a fubar ECU or some such and another recall if none is deserved.

    Brakes are hydraulic but the brake assist is, I believe an electrically driven hydraulic pump with accumulator--I don't know how it works. Likewise for the power steering. But the steering still has its mechanical connection to the front wheels. I think the accelerator is truly 'drive-by-wire' but I thought that was true with Gen II too?
     
  16. qbee42

    qbee42 My other car is a boat

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    True, for both the Gen II and Gen III.

    Tom
     
  17. spiderman

    spiderman wretched

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    That is what I was thinking too. However when it happened to me, my pedal sank all the way down bottoming out on the stop/floor (which made it feel hard).
     
  18. bwilson4web

    bwilson4web BMW i3 and Model 3

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    Temperature at the time(s)?

    Frequency?

    Bob Wilson
     
  19. dva

    dva New Member

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    Just had something similar happen the other day. Was parked at a car wash, they were detailing the outside and asked me to move the car back a few feet. I got in, pushed the ignition, noticed I had not pressed the break yet, so I pushed on the break pedal while the ignition state was in accessory mode, pushed the start button, nothing happened, released the break and went to press on it again and it was frozen solid, just as if someone had put a lock pin in it. I released it, did something else maybe pushed the ignition switch I can't recall and then suddenly the break operated normally again.

    There *is* a setup that can cause this. I'm sure there is a technical explanation of how this can happen, we just need the right technician to answer.
     
  20. garygid

    garygid Senior Member - Blizzard Pearl

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    When SMC1 and SMC2 are both closed, and the stroke simulator is not (yet) active, it seems possible that mechanical pressure on the master cylinder would find that the brake fluid had nowhere to go, and the brake pedal would be high, and not move, even with "strong" pressure.

    Apparently there is some start (or pre-start) sequence that can create this situation.

    With a normal startup, which includes pressurization of the braking accumulator system (you can hear the pressure-motor run when you first open the driver door), it appears that the situation never (or only rarely) occurs.

    If somebody can identify the timing and sequence of events that will recreate the "blocked brake", please let us know.

    Cheers, Gary