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Radar cruise control incident

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by samdaman, Jan 6, 2013.

  1. samdaman

    samdaman Junior Member

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    2011 Five package. 20k miles, no issues in ~1 year. Eastbound on I-78, a few exits west of Allentown PA. Speed limit 65, radar cruise set to 68 and default three-bars [max distance]. All is good for 30 or so miles of rolling hills and light traffic.

    Then, with no change in traffic density or average traffic speed, I start slowing down -- as would be quite appropriate if the driver ahead of me had eased up on the gas. 60, 55, 50, 45. Not quickly -- no where near as quickly as if I were to turn off the cruise -- as though there was traffic slowing down ahead and the radar was just responding to it.

    But the traffic ahead was not slowing down.

    No beeps, no brake assist -- the car just gently slowed down -- in fact, the 'car ahead' icon was still displayed on the cruise indicator -- but in reality, the car ahead was far beyond where 'car ahead' should have been displayed. He was still doing 65 while I was down to 45.

    I was watching behind me -- still wondering if the radar had seen something I was missing -- and didn't really resume active control till cars behind started to get close [I really was concerned the car saw something I didn't!]. As they got close, I just pushed down on the gas -- never de-activated the cruise -- and when back at 60 or so, the cruise again started to act 'normally'.

    Me, not normal at all -- and not sure I will ever use the cruise again...

    Anyone hear of anything similar -- hopefully with a resolution ???

    Thanks
     
  2. bisco

    bisco cookie crumbler

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    have the dealer look at it, should be under warranty.
     
  3. sdtundra

    sdtundra Senior Member

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    Was it raining? Wondering if it was picking up something else.
     
  4. nwprius

    nwprius Member

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    Had it happen to me on a few occasions when there are imbankments or large road signs along side the road in light curves. They do not have to be close but within the distance set on the RCC, ie, three bars, 160 ft. Since it notified me I just added enough pedal to keep it at speed until the RCC took over normally which was almost immediately.
     
  5. samdaman

    samdaman Junior Member

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    To the questions:

    -- I do plan to contact my dealer, as well as Toyota USA directly (it only happened yesterday -- Saturday), but given there are no codes (according to scangauge), I suspect they will just say 'duh?'
    -- there has been no new rain/snow for some days, though we do have patchy snow on the ground.
    -- the highway where it happened is very straight (left/right), but it is an area of 'rolling hills' -- I was almost wondering if that could have been a factor.

    I do plan on re-running the section of highway in question as an acid test, but I probably won't get a chance for a week or so.
     
  6. dhancock

    dhancock 2 Prius Family

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    You got that right! We have had several instances last summer when the DRCC thought there was a car immediately in front, beeped and slammed on the brakes!! Good thing there was no closely following car. My circumstances were quite different, however:
    • Only happened when passing an interstate semi-truck
    • Was traveling at 75mph
    • Only happened when it was hot (near or above 90)
    • A couple of the times (when it was above 90 degrees), the radar "locked up" continually "seeing" (and displaying) a phantom vehicle in front. Turning off the cruse and re-engaging it did not clear the condition (although I could switch the DRCC mode off and just use the regular cruse). I was able to clear it by pulling over and turning the car off. One time, I found that the unit cleared itself as we drove on and the temperature decreased 4 or 5 degrees (below 90).
    Neither the dealer nor Toyota would do anything for me, as it was working perfectly fine when I took it in. I did file a report with the NHSTA on this (though that did not get Toyota to pull their head out of the sand. At the time there were a couple of other similar reports. I'd urge you to fill out a similar report.

    We've continued to use (and like) the DRCC - we just are a little cautious about passing semis when it is hot.
     
  7. annitech

    annitech New Member

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    I would love the DRCC if it were not for the false alarms our unit frequently causes. We regularly drive Melbourne to Ballarat (an hour on divided highway, 100 and 110 km/h limits)and find that the car decelerates strongly at least 5 or 6 times per trip when approaching large road signs, overhead bridges or curves with armco rails, sometimes triggering the beeper and flashing warning in the radar display. Luckily this has not happened when another driver has been following closely - at best, they would think we were crazy. It happens even on the shortest range setting (1 'bar' on the radar display). There is no problem whatsoever with the constant speed cruise control operation.

    I wonder if there is any maintenance/calibration/alignment that can be checked and adjusted on the radar unit? I would love it to work reliably!
     
  8. tumbleweed

    tumbleweed Senior Member

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    I have had a couple of instances where mine picked up the side of a large truck in the other lane, especially if there is a curve, and slowed me down. I have also learned to be careful of cars slowing to turn off in front of me, the DRCC sees the speed difference and slows me down rather quickly. I need to watch for that in case someone is following too close.

    But these things are not really a cause for concern, I drive with my foot near the gas pedal and when it starts to slow without good reason I just push the throttle down a little to compensate until I am past that area. I would say in my car the system errs on the side of safety and has caused me no problems. Overall after using it for 75K miles I am very pleased with it and when I drive a vehicle with normal CC I miss having it.
     
  9. macman408

    macman408 Electron Guidance Counselor

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    Yes, the sensor can be aligned by the dealer. I have had no problems with mine falsely detecting anything.