2010 brake system

Discussion in 'Gen 3 Prius Technical Discussion' started by bwilson4web, Jan 30, 2010.

?

Details on braking anomoly

Poll closed Feb 13, 2010.
  1. Happens in the beginning of braking

    19.4%
  2. Happens after braking for a bit

    79.1%
  3. Had a load in back of Prius

    1.5%
  4. No significant load in Prius

    70.1%
Multiple votes are allowed.
  1. bwilson4web

    bwilson4web i3 and Prime

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    Part of problem diagnosis is to understanding the system so we can map symptoms to potential failure modes. The poll associated with this posting is to ask about subtle items that may or may not have any bearing on the brake anomolies. These are just hypothetical mappings but an important step. One of the best source are Toyota's New Car Features:

    • BRAKE CONTROL / DYNAMIC CONTROL SYSTEMS: BRAKE CONTROL SYSTEM: DETAILS (2010 Prius), Doc ID: RM000004221000X
    • BRAKE CONTROL / DYNAMIC CONTROL SYSTEMS: BRAKE CONTROL SYSTEM: GENERAL (2010 Prius), Doc ID: RM00000421Y000X
    This is just a brief summary of the details.

    OVERVIEW

    The Prius brake system is an integrated system that balances regenerative braking, hydraulic braking, traction control, antilock skid control, and balance into a simple to operate system:
    [​IMG]

    Now one of the symptoms reported is an extended 'loss of braking force.' Considering the curve above, it is likely this is a hydraulic system release. Given the time-scale, this chart suggests the effect occurs in an early braking condition versus a longer, braking interval when regenerative braking force might be a higher percentage.

    It is a fairly sophisticated system that also adjust braking force based upon the vehicle loading:
    [​IMG]

    So one question is whether or not the vehicles experiencing the braking symptoms may have or not had a load in the rear.

    SIGNIFICANT ELEMENTS

    Column 1 Column 2
    0 [th]Assembly[th]Part[th]descriptions
    1 [tr][td]Master Assembly[td]Brake Actuator[td] 4 switching solenoid valves
    2 [tr][td] [td]Brake Actuator[td]2 linear solenoid valves
    3 [tr][td] [td]Brake Actuator[td]8 control solenoid values
    4 [tr][td] [td]Stroke Simulator[td]generates pedal stroke per driver's input
    5 [tr][td]Skid Control ECU[td] [td]manages system
    6 [tr][td]Stroke sensor[td] [td]detects brake pedal operation analog
    7 [tr][td]Speed sensors[td] [td]one for each wheel
    8 [tr][td]Power ECU[td] [td]responds to regen request from skid control ECU
    9 [tr][td]Power ECU[td] [td]sends regen value to skid control ECU
    10 [tr][td]Power ECU[td] [td]controls motive force per skid control ECU
    11 [tr][td]Elect. Brake Dist.[td] [td]adjusts front and rear and left/right braking
    12 [tr][td]Stroke sensor[td] [td]contact type variable resistor stroke position
    13 [tr][td]yaw rate sensor[td] [td]left and right acceleration
    14 [tr][td]acceleration sensor[td] [td] forward and backward acceleration

    Of these elements, I tend to wonder about these sensors:

    • brake stroke - there is history of wiper-based, sensors being a little weak. It is one reason Hall effector sensors are used more commonly.
    • acceleration sensor - something we'll measure with the USB sensor.
    Thanks to the help from those who have experienced the problem, we have a growing list of surface conditions that seem to trigger the symptom:

    You can help by posting photos or Google Street view or Google map addresses of the places this happens. The key to diagnosis will be finding a way to replicate the problem at will. Then we can do things like:

    1. swap Prius - if one vehicle always has the problem and another does not, it means finding out what is different between the two
    2. quantify the problem - we need engineering units that document time, duration and magnitude
    Bob Wilson
     
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  2. georgew

    georgew New Member

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    REALLY appreciative that so much energy is going into researching this.

    FYI, Each time I've had brake loss/pause, there has been zero load in the rear of the car..

    One street near me that would cause brake loss almost every time was caused from what I think was a bulge in the road from a tree root while stopping at a stop sign. Shouldn't be too hard to recreate if we can think of a way to create a similar bump in the road. I've since adjusted my driving habits to avoid this but I'll see if I can get the prius toexperience brake loss at that spot later this week and will take some pictures if i can along with speed, brake force, etc..
     
  3. Airbalancer

    Airbalancer Active Member

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    the only time I have feel anything funny braking is when I have cruise on, it feels like the car is not stopping
    And it could be is I am not pressing hard enough on the pedal to dis engage the cruise, as soon as I press harder it starts to brake
    It think it just a matter of knowing the car better
     
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  4. spiderman

    spiderman wretched

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    Interesting... I have never had the breaking issue (that I know of) but then I have never had a payload either... I wonder if that has something to do with it.
     
  5. FLP

    FLP Junior Member

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    Mine happens at a speed bump as I turn into my cul de sac. I just make sure I'm going very slowly, so that I don't have this occur.
     
  6. qbee42

    qbee42 My other car is a boat

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    Keep in mind that there isn't just one braking issue. Among the possibilities are:

    1) Sticky brakes in reverse.

    2) Soft pedal pressure.

    3) Regenerative braking to friction braking transition.

    4) ABS.

    Some issues may be a combination of the above. Compounding and confusing the various issues keeps these threads lively.

    Tom
     
  7. bwilson4web

    bwilson4web i3 and Prime

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    I'm really interested in the slow-speed, stopping anomalies as these are often close to other objects (aka., bumpers, walls, curbs, walkways.) Also, understand I'm using the "New Car Features," NM1291U, and the "2010 Maintenance Manual," EM1291U, as my source materials. I'm not a Toyota trained technician and my reading and interpretation is likely to have unintended errors. But this is my best understanding ... today ... and I appreciate corrective posts so we can all advance our knowledge and understanding.

    BACKGROUND

    A non-error code, braking anomaly has been reported by some 2010 Prius Chat members:

    • ~18% report "scary, safety issue" (18)
    • ~41% report occurs (40)
    • ~59% report not experienced it (57)
    It seems to be a low speed phenomena:

    • ~47% report speeds 20 mph and slower
    Typical report:
    Modest braking that passes over a manhole cover, railroad crossing, patched surface, or pothole that leads to a longer period of reduced braking.
    Survey From Maintenance Manual

    System architecture:
    [​IMG]

    These are bits that suggest interesting aspects that may apply to our braking system:
    "Do not remove or install electronically controlled brake system parts such as the steering angle sensor, yaw rate and acceleration sensor or brake pedal stroke sensor except when required, as they cannot be adjusted correctly after removal or installation." (BC-1)

    I'm still reading the brake section, over 300 pages. But I wanted to start the conversation. More details to follow.

    Bob Wilson
     
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  8. bwilson4web

    bwilson4web i3 and Prime

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    You could help by giving us a Google address of the speed bump. If there is not Google Street view, take a photo and post it here ... with a yard stick or scale so we can understand the shape. But a simple "me too" post without technical details or even a photo ... wastes everyone's time:

    • ours because we already know something is going on
    • yours because you already knew something was going on
    Please, provide additional technical details and be part of the solution.

    Bob Wilson
     
  9. DetPrius

    DetPrius Active Member

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    Bob, I checked both at the beginning and after a bit as when I made my repeated attempts to recreate it a couple weeks ago, it didn't seem to matter, but this is a gut feel response to the question as I was not looking to answer that specific question. I also checked no load but that is my normal operation of the car.
     
  10. namasteflc

    namasteflc New Member

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    I am disappointed in the Prius 2010 ABS. Although the car does stay straight while stopping in slick snow, the ABS only seems to pulse twice a second. My previous car(Benz) seemed to pulse eight times per second- like going over a series of warning speed bumps. At least i can use front wheel drive to power-steer(the Benz was rear wheel drive). Should i add weight to the rear of my Prius? How much weight? We used to put #80 of salt in the front 'trunk' of our Corvairs- balanced the cars well.
     
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  11. hobbit

    hobbit Senior Member

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    One thing I hope someone does is stick a data recorder on the
    HV battery current sensor, and see what happens there just as
    the sag/transition happens. A real one, i.e. watch the voltage,
    not just logging queries off the OBD-II port. Bet you'll find
    current spikes of over 100A that would be the root cause for
    giving up on regen and falling back to hydraulic.
    .
    _H*
     
  12. bwilson4web

    bwilson4web i3 and Prime

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    I'm still reading the maintenance manual description of the brake system and found these gems:

    • "After replacing any VSC related componets or performing front wheel alignment adjustment, clear and read sensor calibration data." BC-19 - there is a fairly extensive calibration process that covers all of the input sensors. It may require a service order to make sure this procedure is done but given the number of steps, the labor won't be cheap.
    • "If there are no DTCs but the problem still occurs, check the circuit for each problem symptom in the order given in the table below and proceed to the relevant troubleshooting page." BC-32 - Nothing like the symptoms reported show up in the table. However it outlines a significant number of steps including my favorite, checking the connectors.
    • FREEZE FRAME DATA BC-42 - saving the data occurs only when a code is stored. I would not expect anything useful here unless a code is shown.
    • DATA LIST BC-46 - lists the signals that the 'Techstream' can read. This would be great data if recorded during an event. Many sources are dual such as stroke sensor, yaw and accelerometer data.
    • "FR Regenerative Request | 0 Nm to 65536 Nm | Changes according to brake pedal force (When depressing the brake pedal lightly after above 30 km/h (19 mph) or more avoiding sudden braking.)" BC-49 - sound familiar?
    • ACTIVE TEST BC-50 - a way to exercise the braking system components in the bay.
    The rest of the sections cover parts replacement.

    Bob Wilson
     
  13. rachaelseven

    rachaelseven New Member

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    Interesting that this could be tied to the load in the luggage area. The most dramatic occurrence of this I experienced (image 080), which included a noise from the rear brakes sufficient to give the illusion of being tapped from behind, did in fact include a significantly loaded car. We had two good size adults in the front seats (around 350lbs), about 20lbs of gear in the back seat, and about 80lbs of gear in the luggage area. That might be enough to shift the braking distribution toward the rear, which could explain why the sudden application of the friction brakes during the transition caused a noise in the rear end. Just thinking outloud...
     
  14. PaJa

    PaJa Senior member

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    The ABS is working fine. It produce a high freq. gentle pulses. You can not compare it with a regular car (like MB) ABS system.
     
  15. fuzzy1

    fuzzy1 Senior Member

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    My 2010 Prius ABS, on wet pavement, feels much better than my 13-year-old Subaru. So far it has had an incredible grip without the strong pulsation of the older ABS

    As for putting extra weight in the rear, I'll never do that again. Did it once, placing 200 pounds of books (packed for an upcoming move) directly over the rear axle of my last RWD car. While it did help snow traction, it screwed up the front end handling, and likely contributed to me losing steering and sliding off the road. That car had a light tail, but it was supposed to be that way. Changing the weight distribution only made things worse.

    Now, any heavy loads are pushed forwards towards the middle.
     
  16. DetPrius

    DetPrius Active Member

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    I suspect the ABS has the ability to respond in more than one way. I've read several reports of very gentle and quick pulses on the brake. My experience on ice is that it pulses maybe twice a second, which is slower than I've experienced in other cars. The pulses were VERY coarse and VERY noticeable. I've seen at least one other poster with the same description I just gave. I also found that it's possible to lock up the wheels, in light regen braking, on ice and NOT have the ABS kick in. More pressure on the pedal activated ABS.
     
  17. Ivey1982

    Ivey1982 New Member

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    I just joined this forum to add my similar experience with a Prius 2010 this past Dec. 2. I rented from Avis in Montreal for a trip to Quebec City, with no luggage and I was the only passenger. Coming to a red light I applied the brakes as normal, but I hit one of our many bumps in the road and the car immediately accelerated as if brakes were not applied. I had to jam on them to barely avoid hitting the stopped cars in front of me. I would never recommend this car to anyone especially as there is no recall mentioned or fix for this problem that I have heard about.








     
  18. bwilson4web

    bwilson4web i3 and Prime

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    You can help be part of the solution by providing a street address of this bump ... something we can use Google Map and Google Street View to see what it looks like. Otherwise, it is just another "me too" posting with no contribution to the diagnosis.

    Bob Wilson
     
  19. PaJa

    PaJa Senior member

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    do not know rent a high tech car without an experience. If you jam on brakes you had done what was correct in that situation.
    You have to know you are driving the computer operated car and each software code has a one bug minimally ;-)
     
  20. bwilson4web

    bwilson4web i3 and Prime

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    So looking at the technical content of your posting:
    Have I properly quoted how much technical content was in the posting? OVer in the main forum are several brake threads and that is an excellent place to vent your spleen.

    Provide facts and data such as a location that you've experienced the problem; specific configuration; or something of value. Otherwise, I might as well <PLOINK> your username.

    Either be part of the solution or remain part of the problem ... noise distracting us from hard, engineering data.

    Bob Wilson

    ps. The <PLOINK> refers to our ability to add folks to the "ignore list" under UserCP. Sometimes, you just have to 'turn up the squelch' to concentrate so serious postings show up. My general rule, three strikes and 'your out.' ... As my drill instructor said, "Don't get mad, get even."
     
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