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TACC failure

Discussion in 'Model S: User Interface' started by Boatguy, Jun 28, 2016.

  1. Boatguy

    Boatguy Member

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    I was driving home today in local traffic on a local four lane (two each direction) with the TACC set at 40mph. The TACC indicator was blue and the AS indicator was gray. In front of me a motorcycle changed lanes and took a position behind a car. Beyond the car I could see the next stop light was red. I knew the TACC would respond slower than I would (it doesn't look as far down the road) and waited. Then I saw the motorcycle appear on the display and felt the car begin to decelerate since both the motorcycle and car in front of it were slowing for the red light.

    Then I felt the car stop decelerating, looked down, and saw both the TACC and AS icons disappear entirely from the display. The TACC icon didn't just turn gray, it disappeared entirely. I immediately manually braked and there was no serious safety issue.

    After the light turned green, I moved on with traffic, both icons appeared gray and I re-engaged TACC with no issues.

    However, this makes me reconsider two recent situations:

    1) The woman driving north of Los Angeles who said TACC failed to stop the car and she rear ended someone. Tesla said the TACC was not engaged. Had I not been paying close attention, the same thing would have happened and Tesla would have said that TACC was not engaged.

    2) The German driver who hit a stalled car seems like another situation I would now like to understand better.

    I almost always use TACC on local streets and the freeway, excluding merges, exits, big intersections, etc. I consider it a good way to stay with traffic and not rear-end anybody. But something happened today that ensures I will be keeping a close eye on those icons.

    Firmware: 2.22.50
     
    • Informative x 1
  2. ecarfan

    ecarfan Well-Known Member

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    I don't have TACC on my "classic" S but have used it on my fathers car. When TACC is engaged, and then turns itself off for whatever reason, is there an alert sound?
     
  3. chillaban

    chillaban Member

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    I wish TACC would also have a audible tone with it being engaged vs disengaged. It is really easy to lose track of the TACC state, and I've accidentally tapped the brake pedal before trying to rest my foot and it disengaged TACC.

    However, I've found that even under regen acceleration in that case, collision warning still does kick in, so I'm not sure what you have to do (probably a firm brake press + release) to deactivate collision warning.


    Just this morning, I canceled TACC in the city by tapping the brake and activated regen coming up to a red light. I was greedily trying to get a bit more regen, and to my surprise, collision warning sounded due to the rate at which I was approaching a stopped car. Of course I was paying attention and able to smoothly intervene without incident.
     
  4. Boatguy

    Boatguy Member

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    I know there is a sound when AS is engaged, but I don't think there is one when TACC is engaged or disengaged. There was no sound this afternoon, I just felt the car stop decelerating.

    I've also heard the collision warning, and then it lights up the target in red. I had it do that yesterday when the road made a fairly sharp left and it decided I was going to hit a parked car; which of course didn't happen because I followed the road. I also hear that warning when driving in the left lane of a boulevard when there is a lot of vegetation in the median projecting into the lane a bit. The side sensors pick it up and warn that a crash is imminent.
     
  5. DoubleE

    DoubleE Member

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    In my experience, there was one time the car sounded all alarms and flashed the instrument panel in red with 2 large hands on a steering wheel, with a message that said take over immediately. It was significantly large --- not just the typical "place hands on steering wheel" warning.

    I assume it would do the same in that instance?

    I believe my alarms went off when the AP could no longer track the lane markings and there was no car in front of me.
     
  6. chillaban

    chillaban Member

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    This happens when AP (Autosteer) is imminently going to disengage, but it does not happen for TACC engaging/disengaging.
     
    • Helpful x 1
  7. mikeash

    mikeash Active Member

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    I'm not aware of anything that would cause TACC to disengage by itself. Is there any chance you might have bumped the brake pedal or cruise control stalk by accident?
     
  8. Saghost

    Saghost Active Member

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    Wait. What alerted you to this was the car stopped decelerating? How do you have the regen level set in the car settings?

    If it's set to normal, I would have expected any loss of TACC to produce immediate heavy deceleration - the full 60 kW of regen.

    Even set to low the car should be decelerating, though not very quickly.
     
  9. Boatguy

    Boatguy Member

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    I don't think so. I'm very experienced using TACC because it's ACC on my i3 and I've been using it for a couple of years. And I've been a regular cruise control junky for years. The stalk is actually a bit of a pain for disengagement, it was the same stalk on my MB. What really caught my eye was seeing the two icons disappear.
     
  10. Boatguy

    Boatguy Member

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    Regen is set to normal, but TACC was decelerating for the motorcycle and car stopped ahead.

    Certainly if I was just cruising along then yes, a loss of TACC would cause regen to kick in, but the car was already decelerating. That sort of begs a question (at the risk of hijacking my own thread) of whether TACC is able to use more aggressive regen than the standard setting. At the point it cut out I was probably doing less than 30mph. Certainly it eventually is using the friction brakes and not just regen. In this situation I clearly felt the car "release", which could either be just less deceleration, or actual free wheeling. It happened fast and I immediately went for the brake pedal.

    I'm quite hesitant to start screaming "TACC failure causes accident", but something happened, and it was not driver initiated. If I had hit the car in front of me, Tesla would have quite accurately said that the TACC was not active, because it was not. But I've never seen the TACC just abort like that.

    Bumping the stalk or the brake pedal would explain it all, but this is a street I routinely drive and nothing odd was going on. I was actually watching kind of closely to see if the TACC would pick up the motorcycle, and an instant after it did, it aborted.
     
  11. mikeash

    mikeash Active Member

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    I glossed over the fact that the TACC icon completely disappeared. I don't think I knew that could happen. That definitely seems to indicate something very strange happened, but I have no idea what it might be.
     
  12. mmccord

    mmccord Member

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    Yes, double red hands. It comes on when any if the following things happen:
    1) TACC loses confidence enough to give up
    2) speed exceeds 90mph
    3) the small computer screen is rebooted (it shows up on the 17" display in this instance)
    There might be other triggers, but those are the ones I've run into.
     
  13. tkizzy

    tkizzy Member

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    TACC has been mostly awesome (I'm still only on the trial), but I've had only one situation where I felt like if I didn't take control and brake it would have been no Bueno. I was demonstrating autopilot on a street with a fairly sharp bend in the road, and so the car in front was at enough of an angle that the car didn't think there was anyone in front of me, but autosteer was still functioning. Perhaps it would have worked as the car came around the bend with just a slightly harsher than normal braking experience, but I didn't wait to find out. I realize this is in no way an intended use case as was made clear before enabling autopilot features. But probably a useful datapoint for Tesla engineers nonetheless.

    PS LOVE LOVE LOVE AUTOPILOT.
     
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  14. chillaban

    chillaban Member

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    You did the right thing by taking over decisively when the car didn't do something that made you comfortable. That is the key difference between your story and those that end in a crash :)

    It's pretty easy to supervise Autopilot even in roads it's not intended for.
     
  15. msnow

    msnow Active Member

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    Never heard of this specific thing happening to anyone before including the rear end collision last year you referenced. That scenario was different from yours. The fact that you lost the grayed out icons is very strange. Strongly suggest you document this as soon as possible in an email to Tesla including date and time of incident. It will benefit all of us.
     
  16. Boatguy

    Boatguy Member

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    Good idea. I sent an email to ServiceHelpNA which I guess is where you send stuff like this. If not, please advise.
     
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  17. DoubleE

    DoubleE Member

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    You should have reported a bug using the voice recognition. Maybe their team would look into it.

    I randomly report stuff just in case.

    Better for them to have more information than less.
     
  18. Boatguy

    Boatguy Member

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    I got a response this morning from Tesla asking for more details. Presumably they will look at the logs and send me some sort of reply. I'll post whatever I learn.
     
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  19. msnow

    msnow Active Member

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    That's excellent. Was the call from Corporate or your local Service Center?
     
  20. DoubleE

    DoubleE Member

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    Good to know they are taking this situation seriously, and are actively investigating. Definitely keep us posted on the outcome.
     

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