Unintended Cruise Control Acceleration?

Discussion in 'Prime Main Forum (2017-Current)' started by RustyRaven, May 6, 2020.

  1. RustyRaven

    RustyRaven New Member

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    2020 Prius Prime. Acceleration behavior changed from 2006 Prius? ...
    (This question is *not* about dynamic/adaptive cruise control.)

    Yesterday I was using cruise control at a steady speed. I was not following any cars. Single lane highway. Clear, sunny weather. I held the cruise-control lever up for a few seconds and then released it. Initially I did not notice much speed increase. But steadily -- *AFTER* I had released the lever -- the vehicle continued to accelerate. I was very surprised to see the car continue to increase its speed well beyond my steady speed.

    Today I experimented. From steady 45 mph, I held the lever up and counted to 10. Released the lever. Waited. The car accelerated to 70 mph over the next 15 seconds or so -- *after releasing the lever*. Wow. Is this how it is supposed to work? On previous Prius/Highlander models, when you release the upward pressure on the lever it stops accelerating. This seems dangerous.
     
  2. Tideland Prius

    Tideland Prius Moderator of the North
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    Yes. This is related to the dynamic/adaptive cruise control and it is operating correctly.

    Watch the MID. It will tell you what speed you're setting it to. Lifting and holding will incrementally increase the speed (originally, it's 1mph per tap and 5mph when you hold... I think that was changed to 1mph even when holding because of the scenario you described and people freaking out about it accelerating to a higher speed).

    DRCC will indicate the set speed in the MID. You tell it what speed you want and it'll get there (using the radar as a guidance whether there is a car or not in front of you).
     
  3. mistermojorizin

    mistermojorizin Active Member

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    that's normal. you set the speed and then the car gets to that speed. you can change how quickly it gets there by changing drive mode (so in pwr mode, it gets there quick, in eco it take a while). So set your speed, set your distance and wait for the car to get there.
     
  4. FuelMiser

    FuelMiser Senior Member

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    This is just the way the CC works in the Gen 4. And totally different from earlier Gens. When you're holding the CC lever up to advance the speed, you need to be watching the CC display in the middle of the display paying attention to the displayed MPH. Not the car's MPH, the CC's. Release when it reaches the desired speed. A better way to do it is bump the CC lever up instead of holding it up. Each bump will increase the set speed 1 MPH!
     
  5. The Electric Me

    The Electric Me Go Speed Go!

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    Maybe read your owners manual.
     
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  6. Salamander_King

    Salamander_King Senior Member

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    Not sure how CC worked on 2006 Prius, but at least for Gen3 and Prime, it seems to work as others described. Quick single flick for 1mph increase or decrease, or hold longer to get more increment. I always use single flick to increase or decrease. If I need to go much higher or lower, then I do multiple flicks in succession.
     
  7. RustyRaven

    RustyRaven New Member

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    Thanks! That works. I've just had the car a couple weeks and still getting used to all the messages on the dashboard.
     
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  8. Tideland Prius

    Tideland Prius Moderator of the North
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    It depends on whether you're in DRCC mode or regular CC mode. If you went into regular CC mode on the Gen 4/Prime or Gen 3 with DRCC, it'll operate like the old CC where it will increase/decrease speed until you release the stalk. But DRCC works differently since you can see the set speed on the MID and thus you can choose the set speed visually and then the car will do its thing. This is because you can change the set speed to adjust to the current environment (i.e. traffic or construction) without cancelling CC. (e.g you set the speed at 70mph, you enter a construction zone following someone ahead so you both slow down to 40mph but the DRCC is still set at 70mph. For me, sometimes I might drop the set speed to 50mph just so I don't get a sudden acceleration if the guy in front changes lanes but it doesn't change the fact I'm still doing 40mph following the guy ahead).
     
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