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What does PCS (Pre-Collision System) do with the accelerator?

Discussion in 'Gen 4 Prius Main Forum' started by Colin Jones, Nov 15, 2016.

  1. Colin Jones

    Colin Jones Member

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    OK - so we know that PCS will try to avoid a collision by automatically applying the brakes if you don't react, but does anyone know what it does with the accelerator? If you kept your foot on the accelerator when PCS kicks in the automatic braking, does it cut power to the engine at all, or does it just apply the brakes at the same time as keeping the acceleration going?

    Just a thought that occurred to me! (for example what if someone goes unconscious while driving) :)
     
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  2. alanclarkeau

    alanclarkeau Senior Member

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    Interesting question. Hopefully I won't try it. BUT - I remember the manual talks about something like pressing the accelerator abruptly as well as abrupt steering movements will disable the system.

    Not sure what would happen if the accelerator is already down hard. Have you checked the Manual?
     
  3. raspy

    raspy Senior Member

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    From the manual;

    "The pre-crash braking function may not operate if certain operations are performed by the driver. If the accelerator pedal is being depressed strongly or the steering wheel is being turned, the system may determine that the driver is taking evasive action and possibly prevent the pre-crash braking function from operating.
    ●In some situations, while the pre-crash braking function is operating, operation of the function may be canceled if the accelerator pedal is depressed strongly or the steering wheel is turned and the system determines that the driver is taking evasive action."

    Oh, the manual also recommends turning off PCS before you drive the car in a sporty manner.
     
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  4. Colin Jones

    Colin Jones Member

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    Yeah - it still doesn't say what it would do if the accelerator is just being held in it's "normal" position though... i.e. does it cut the accelerator while braking (unless you then depress it hard), or continue running the engine at the same speed while braking. At a guess I'm assuming it will cut the accelerator to brake...
     
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  5. Tideland Prius

    Tideland Prius Moderator of the North
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    Perhaps the Drive-Start Control will take over? i.e. it'll reduce accelerator input while braking.

    Hence the "if may cancel if you depress the accelerator strongly". If you don't, it'll reduce power output.
     
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  6. kithmo

    kithmo Couch Potato

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    I would err on the side of caution and say it doesn't function. I would think that if you black out your foot would relax and come off the accelerator anyway, unless you have very heavy feet, the pedal has a return spring on it.
     
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  7. raspy

    raspy Senior Member

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    I really need to find an empty car park, erect some cardboard cutouts and conduct an experiment. I really want to know what happens.
     
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  8. RCO

    RCO Senior Member

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    Just don't forget to put tin foil over the cut outs. It's said that it doesn't detect cardboard very well!
     
  9. Priifan

    Priifan Member

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    Please add what happens when the car is on cruise control and another car suddenly pulls in front of it. It doesn't seem to matter much whether the distance ahead is set at 1, 2, or 3 bars. The car seems to slow down at different times even when there is no one ahead in my lane. And then does it try to tell me what speed would work under those conditions? Definitely tricky when you combine two or more features. Heeelllllpppppppp!
     
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  10. kithmo

    kithmo Couch Potato

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    Mine seems to only slow down if a car pulls in front then brakes or slows down quickly.
     
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  11. Sam Spade

    Sam Spade Senior Member

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    The "throttle" is not a mechanical link but is computer controlled; fly by wire kind of.
    Put your vehicle in Park and press the "accelerator". Notice that nothing happens.
    I believe putting it in Drive with your foot firmly on the brake will also keep the engine from responding to accelerator input.
    It would be rather stupid of them to slow the vehicle (dramatically) without taking power off of the engine.
     
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  12. alanclarkeau

    alanclarkeau Senior Member

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    Check it out - in PARK, accelerator will still rev the engine - not to the extent of a traditional car, but definitely does.
     
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  13. Sam Spade

    Sam Spade Senior Member

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    Apparently all models are not designed the same.
    My C does NOTHING if you push the gas pedal in Park.
     
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  14. RCO

    RCO Senior Member

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    Nor my Gen 4 Business Edition (bit like a US 3) in neutral with P, accelerator would not bring on ICE.
     
  15. alanclarkeau

    alanclarkeau Senior Member

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    I started it, left it in P(ARK), not neutral, pressed the accelerator and the ICE revved up - not much, probably only 12-1500rpm I'd guess, dropped back to idle when I released accelerator.
     
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  16. RCO

    RCO Senior Member

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    Ok, my bad. I had park selected, so it would have taken me out of neutral, but the car was in ready mode.