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Unexpected auto braking

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Earman, Nov 12, 2011.

  1. Earman

    Earman CDN Prius III Technology Blue

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    I have had my Prius for over a year and this has never happened to me before. Two days ago, about 3 minutes after starting driving, the display switched to a rectangle with BRAKING written in the middle with rapid beeps. This flashed very briefly on the display and nothing else happened. There was no one in front of me at a close distance and the cruise control was not engaged. I discarded it as a fluke.

    This morning the same thing happened again but this time the display flashed a bit longer. Again there was no traffic reason for it and nothing else happened.

    Tonight, I was driving on the Burrard bridge at about 60K/h. The car in front of me was quite far ahead from me and there was no one in the next lane which could cause me to want to apply the brakes. Suddenly the display flashed BRAKING again, along with fast beeping. After a very brief period, the seat-belts suddenly tightened and the brakes were applied briskly without me doing anything! My foot was still on the accelerator. the "emergency" braking lasted a couple of seconds, then the display returned to normal and the Prius stopped braking resuming normal behavior.

    I was lucky the car behind me was not tail-gating otherwise I would have likely been hit. There was absolutely nor reason for me to apply the brakes harshly like this at that particular time, the bridge was almost empty of traffic.

    I guess that if I had been rear ended the driver would have said that I had accidentally applied the brakes without any reason, instead of the accelerator, and that I was trying to blame it on the Prius software...

    This scared the hell out of me and my wife is afraid to go back in the car! It could have been catastrophic if I had been on the highway at 110K/h...

    I guess this is related to an accident detection system, but

    1/ I did not think I had that feature on my Prius
    2/ the cruise control which has a distance radar sensor was not turned on
    3/ there was no car in front of me, or on the side of me, which could have been too close and causing a potential risk of collision. I basically had plenty of space all around me at the time of the totally unnecessary and dangerous "automatic" emergency braking.

    I am of course going to take the car to Toyota after the week-end. I don't know if they will be able to do anything as it is an intermittent problem... I am wondering if this has happened to other people before and if it is a known problem?
     
    #1 Earman, Nov 12, 2011
  2. F8L

    F8L Protecting Habitat & AG Lands

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    That interesting. I've never heard of this issue. If it's related to the accident avoidance system could there be something blocking the sensor intermittently? It's definitely something that needs to be taken care of before someone gets hurt. Please keep us updated!
     
    #2 F8L, Nov 12, 2011
  3. cproaudio

    cproaudio Speedlock Overrider

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    I think all the Prius with radar cruise control has this system. You can turn off the active braking via push button switch on the black panel under the driver dash. It won't turn off the "BRAKE" warning so the anti collision warning is still there and working but it will turn off the self braking.
     
    #3 cproaudio, Nov 12, 2011
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  4. dustoff003

    dustoff003 Blizzard Brigade #003

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    That is the Pre Collision System engaging uneven pavement or bridge expansion joints may set it off. It happens to me on one bridge that I cross sometimes if I am in the left lane the PCS will quickly go off then realize there is no collision hazard. In the right lane I get no accidental engagement, the expansion joint is the problem. Read the section of your owners manual for the PCS it will go over what may set it off and explain how it works. There is also this thread on your topic.

    http://priuschat.com/forums/gen-iii-2010-prius-main-forum/69375-pre-collision-system-activation.html
     
    #4 dustoff003, Nov 12, 2011
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  5. Earman

    Earman CDN Prius III Technology Blue

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    Thanks for the info! I had not found the thread on pre-collision as I had only searched for "braking". It explains a lot.

    I am going to disengage the braking part as the warning and pre-tension of the belt should be enough. I don't want to risk an accident to try prevent one from possibly happening!

    Thanks again for making this clear for me, I feel much better now!
     
    #5 Earman, Nov 12, 2011
  6. macman408

    macman408 Electron Guidance Counselor

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    Yeah, definitely take it to the dealer - as long as you don't drive lots of miles, you should still be under warranty. Before you take it though, make sure the Toyota emblem on the front of the car is clean, and there's nothing in the space immediately behind it under the hood and in front of the radar sensor (right behind the emblem, has a flat face pointing out the front). Otherwise, maybe it's out of alignment, and pointing a bit too far down, or to one side or something? I believe they have a procedure to calibrate it with some special tools to make sure it's pointing exactly in the right direction.
     
    #6 macman408, Nov 13, 2011
  7. Bill Norton

    Bill Norton Senior Member

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    Something that it could be is some A-hole on the road ahead of you is running a thoroughly illegal Radar or GPS
    (or godknowswhat kind of homemade) Jammer.
    This could be a job for the FCC and FAA if this were the case.
    You can look up cases like this.
    There was a NJ airport that would routinely see a degradation of the GPS signal.
    Eventually they tracked down a truck driver with a powerful GPS jammer.
    I have no idea how you could get the Feds to survey the highways near you for this....
     
    #7 Bill Norton, Jan 26, 2013
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