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Strange Traction Control Behavior/activations

Discussion in 'Prime Care, Maintenance and Troubleshooting' started by Marco Morel, Aug 1, 2019.

  1. Marco Morel

    Marco Morel Junior Member

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    I have had a recurring strange issue with my 2018 Prius Prime since about 14,000 miles. (Currently has 30,527 miles on it) it seems that while I have the brakes applied and I hit a bump the TCS system activates and releases all brake pressure then quickly grabs again. I shrugged it off but today it almost caused me to rear end someone. I was going down a hill at about 30 miles per hour and there was a crack in the road that they had filled and it left a little bit of a raised edge in the road. I was following behind someone and applied the brakes I hit this little crack and my traction light began flashing and the brake pressure was released causing me to gain speed (rather quickly) almost into this guy's GMC Acadia. I then pushed the brake farther and the Traction control disabled and the car responded and I was able to avoid hitting him. This has happened 3 times and it's beginning to get concerning. This can't be the way the TCS system is designed to behave it also seems strange that TCS has the ability to completely remove brake pressure from you. I will say that each time the car recovered rather quickly and re applied the brakes but I'm wondering if this is something someone else has experienced. Between this, the auto high beams failing exactly a year after I bought the car, and rust forming under the handle of the trunk release button. I'm questioning what happened to Toyota? My 2010 never had any of these issues and also any issues that it did have Toyota was more than happy to help, now...not so much
     
  2. Bob Comer

    Bob Comer Active Member

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    I think all the cars I've driven with a TCS have acted like that, including my 2010 Prius. If you're going fast enough to make the wheel bounce a little, it's enough for the car to think it's slipping. Heavier brake pressure is what i do when it happens. If it's something like raliroad tracks, which I cross more than once each commute, i tend to brake before and after the tracks, and not when i'm going over them...
     
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  3. Marco Morel

    Marco Morel Junior Member

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    Yeah it's just really strange. All the other cars I've owned (2010 Prius, 2014 Kia Sorento, 2015 Camry, and I've driven many rental Corolla's) have all been driven at the same speeds on the same roads and I remember hitting a very big bump in my Corolla while braking and TCS didn't intervene once. I think your right though it seems like the Prius computers are much more sensitive than literally any other Toyota vehicle and they respond very differently. I guess I shouldn't worry about it too much but it's still just something that is of concern. I guess because the Prime weighs more than the normal Prius and most other Toyota sedans it has more weight on it's suspension and it can cause more accidental activations of TCS which would make sense
     
  4. Blauer Glimmer

    Blauer Glimmer Active Member

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    My 2017 Prime behaves the same way, as did my Gen2. My auto high beams seem fine, but I barely use them. There are many posts about the rusted handle on this forum.
     
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  5. sam spade 2

    sam spade 2 Senior Member

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    Did this convince you that you were following too close ?
    It probably should have.
     
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  6. Vman455

    Vman455 Senior Member

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    Gen 3 does the same thing; this is my first car with traction control, so I can't say anything about its behavior in relation to other cars'.

    It used to do this all the time on one pavement heave just south of downtown; thankfully, they repaved the road last year.
     
  7. Tideland Prius

    Tideland Prius Moderator of the North
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    Gen 2 and 3 does the same thing. It’s annoying and disconcerting. (Happens on railway crossings and wet manhole covers too).

    I had my first occurrence with the Prime just recently. I felt like it responded faster than the last two Prii- in that it braked again after releasing much quicker than previous models. It’s all subjective of course since I don’t have video evidence to review and time stamp the experience.
     
  8. Flaming

    Flaming Active Member

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    Even if i know the hydraulic brake are not engaged ( thanks to Hybrid assistant ) i always release completely the brake pedal for a fraction of a second when i slow down and roll over a Manhole cover ( if i can't avoid it ) .. the metal cover is much more slippery than the road. The regen is very strong .. so i guess that any cracks , bump ...etc ...will cause the traction light to flash.

    I suppose the regen brake need a good grip with the ground so if the wheel jumps the traction control kick in .. to help you to keep the car straight and also to protect the hybrid system.
     
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  9. Marco Morel

    Marco Morel Junior Member

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    I was actually following as close as the ACC was letting me at the 3 bars setting. I don't like using cruise downhill (even though the Prius has a much better ACC system than most cars) so I disengaged it with the brake pedal and continued applying the same pressure. He began slowing down to turn and if TCS didn't have its little episode I would have stopped with plenty of room to spare but because of the very steep downhill (Iowa actually has VERY ungodly hills in some areas) when TCS took my brakes away even for the half/full second that it did I gained speed very quickly therefore ALMOST hit him.
     
  10. Marco Morel

    Marco Morel Junior Member

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    Yeah it's not the camera that failed but the cheap little button that Toyota puts to enable/disable the system is the culprit it was a very big problem in their Highlanders. My hypothesis is that Toyota has it positioned where your knees are and sometimes when I get out of my vehicle one of my knees will rub/knock the panel which the button sits and therefore it causes problems.
     
  11. NSXT

    NSXT Active Member

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    Have you tried using B mode for steep downhill?
     
  12. jerrymildred

    jerrymildred Senior Member

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    One thing that I'm sure contributes to this behavior is that so many of us run our tires at higher than typical pressures. This makes them less able to conform to those small bumps and more likely to hop over them.

    Another thing is just for clarification. It's not traction control doing this, it's the ABS. Traction control applies braking to wheels that are starting to spin. ABS removes braking from wheels that are starting to skid.

    And, as mentioned earlier, if you almost hit someone because of this, you're not leaving enough distance. If that driver slammed on his brakes for something he saw but you didn't, you'd be calling the insurance company and paying for a ticket.
     
  13. sam spade 2

    sam spade 2 Senior Member

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    That sounds like making excuses to me.

    Regardless of WHAT the details ARE......if you almost hit the vehicle ahead, they you WERE following too close.

    AND.....I personally think that using the cruise anywhere but on a limited access or controlled access highway is a DANGEROUS habit to get into, as your story here tends to indicate.

    ALL KINDS OF UNEXPECTED THINGS CAN HAPPEN. The quirk with the brakes is but one.
     
  14. Marco Morel

    Marco Morel Junior Member

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    The reason ACC was still active was because the way the road works is this. 55 mph (had cruise set to 60) then you enter a weird part where you pass a gas station and 2 houses but the speed limit does not get reduced so no need to disengage. The GMC began to slow down before he hit the hill because his turn is right after you get down from the hill. ACC began slowing me down but also seeing the hill I disengaged it PRIOR to getting on the hill. I slowed down to about 25 miles per hour and began descending where he was still slowing down to make the turn. I pressed harder on the brake and at about 15 miles per hour the TCS system had activated and disengaged it was only for about half a second so I gained speed but it quickly recovered by then the Acadia was pretty much in the other lane completing his turn. So if I would have hit him at all it would have been very minimal. Keep in mind he didn't use a turn signal until the bottom of the hill so I thought he was going to still go straight at the bottom it caught be off guard and whatever. I didn't hit him and my Prime is still happily in the garage charging right now so whatever it's fine. I came here to get an answer to (what I thought) was a problem not get dogged on about my driving
     
  15. Marco Morel

    Marco Morel Junior Member

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    Okay (sorry for so many questions) I just want a better understanding of this car. I've only owned 1 Prius before hand a 2010 and it was the absolute basic model you could get so stepping into the Prime is like a technology heaven.
    So does the traction light flash when ABS activates? ABS has activated twice in my 2010 and it made a sound but it didn't flash anything or do anything on the guage cluster (I would imagine maybe Toyota changed it in the 4th gen)
     
  16. m8547

    m8547 Senior Member

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    I think the answer is, sometimes.

    I can definitely see how if you're expecting dry pavement braking distance, but the ABS decides it thinks the road is really slippery because you just hit a bump, you might have a close call trying to stop in time.

    I haven't done many hard stops because eco driving, but the times when I have, braking in the Prius doesn't exactly inspire confidence.
     
  17. Marco Morel

    Marco Morel Junior Member

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    Yeah, the Prius has never been strong in braking performance. I'm pretty sure every gen of Prius has had some issue with braking. I still Iove the car though.
     
  18. jerrymildred

    jerrymildred Senior Member

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    do not know. I'd have to look that one up in the manual. I've never needed ABS in the Prime yet. But I have needed it in other cars because in FL it's typical to not pull out from a cross street or driveway until the traffic is within a few yards. When that happens, I am NOT looking at the dash to see what lights are on. Too busy estimating rate of closure and escape possibilities. When that happened, the buzz in the brake pedal told me the ABS was active.
     
  19. sam spade 2

    sam spade 2 Senior Member

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    Sometimes what you WANT is not what you NEED.

    For instance, if you were able to distinguish which light on the dash was flashing ......when you were about to hit the car ahead of you......your attention was in the wrong place too.

    Cheers.
     
  20. ChapmanF

    ChapmanF Senior Member

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    Not in my experience, no. The traction light will flash when the traction control activates, which is a related but different function, also handled by the same ECU.

    Also, one of the all-time most frequently asked new-Prius-owner questions ever isn't really about the traction control or the ABS actuating, but simply the car transitioning from regen to four-wheel braking so that it will be able to escalate to ABS later if it needs to.

    Typically, no light blinks for that, unless the road condition that brought it on was extra squirrely.
     
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