"BRAKE!" Warning Light While Turning Left At Intersection

Discussion in 'Prime Main Forum (2017-Current)' started by hox, Dec 20, 2020.

  1. hox

    hox Junior Member

    Joined:
    Mar 25, 2009
    15
    10
    0
    Location:
    Portland, OR
    Vehicle:
    Other Non-Hybrid
    Hello, I purchased my 2020 prime limited in March and have only put ~2600 miles on it. I live in Portland, OR and it has been very rainy this week. Today my prius did something unpredictable and very dangerous had my circumstances been a little different. I was at an intersection with a traffic light and a left turn lane that uses a left turn arrow. I was finishing up some errands running solely on EV and the battery had exhausted and the ICE had kicked on about 1/4 mile to this intersection. I stopped in the left turn lane and thankfully no-one was behind me. When the green left turn traffic arrow came on I gave the car gas and was met with a sudden stop, a red all caps BRAKE sign popped up on the dash. I could not get the car to go into park so to get going I had to turn it off, depress the brake and hit the start button. I waited out the traffic light to cycle through again proceeded to turn left and go home.

    I thought this behavior was built in as a safety feature to prevent a collision. I was alone in the intersection there were no other cars or pedestrians near me, so could water/rain have affected this system? The sensors are clean and I have not had any warnings in a few days since I was told by the system to clean the sensors. This is very concerning to me because the sudden unpredictable stop would have certainly caused some one behind me to rear end me. I see no CEL or error codes so I don't have any idea what is causing this. Going to the dealership is a 45 min drive but I will do this is that is what folks recommend.

    As a side note, could the fact that I had exhausted the battery and had just activated the ICE caused this issue?

    Thanks in advance for any suggestions or thoughts.
     
  2. AldoON

    AldoON Junior Member

    Joined:
    May 24, 2020
    95
    67
    0
    Location:
    Milton, ON
    Vehicle:
    2018 Prius Prime
    Model:
    Upgrade
    I would take it to the dealer... That shouldn't happen. Do you have a dash cam?
     
  3. hox

    hox Junior Member

    Joined:
    Mar 25, 2009
    15
    10
    0
    Location:
    Portland, OR
    Vehicle:
    Other Non-Hybrid
    Unfortunately, I do not use a dash cam. Thanks for your thoughts
     
  4. davecook89t

    davecook89t Senior Member

    Joined:
    May 10, 2016
    975
    711
    0
    Location:
    Washington State, Florida
    Vehicle:
    2017 Prius
    Model:
    Four Touring
    I believe there is at least one other report of a similar incident by a member of this forum, but that post appeared some time ago and I don't believe I will be able to find it now. I'm sure it is upsetting when it occurs, and I would also advise having the car checked out at the dealer and explaining to them the circumstances under which it happened.

    I am still of the opinion that the Emergency Braking System prevents more accidents than it causes, but if you happen to be the person where it actually causes an accident, that is of little consolation. I can attest to the fact that the system saved me from having an accident at least once. The time that sticks in my mind was an occasion where I was making a legal U-turn at an intersection and another car was making a right turn from the crossing road to my left. We almost collided and I believe we would have, had my car not applied the brakes with the big red BRAKE! warning. I was quite impressed that the system detected the other car, even though it was more to my side than directly in front. I believe the other driver would have been more at fault, having probably made his right turn without stopping, but I was nevertheless pleased to have avoided the collision.
     
  5. Tideland Prius

    Tideland Prius Moderator of the North
    Staff Member

    Joined:
    Oct 2, 2004
    42,212
    13,761
    41
    Location:
    Canada
    Vehicle:
    2018 Prius Prime
    Model:
    Technology
    That is very odd. Being in Hybrid mode shouldn't affect PCS as it's completely independent so there must've been something that either the radar or camera picked up. Additionally, you have ICS on your Limited which could also activate if by sheer luck, a racoon or similar sized animal walked in front of the car and the sonar picked it up (so it was ICS rather than PCS).

    I have never had PCS brake for me even when the BRAKE! flashed (usually if a car is slowing down to turn or to change into the middle lane that allows turning in each direction and I keep going at the same pace).

    So far, 100% of the time that the car stopped, it was ICS that braked (especially if I'm squeezing into a tight parking spot and it's sensing the wall or the car behind or in front).
     
    Gokhan and Raytheeagle like this.
  6. schja01

    schja01 One of very few in Chicagoland

    Joined:
    Apr 22, 2005
    1,384
    953
    0
    Location:
    Chicagoland
    Vehicle:
    2018 Prius
    Model:
    Prime Advanced
    Not being able to clear the condition short of recycling the vehicle should be treated as a major issue.
     
  7. vvillovv

    vvillovv Senior Member

    Joined:
    Mar 19, 2013
    1,486
    548
    0
    Location:
    NY
    Vehicle:
    2017 Prius Prime
    Model:
    Prime Plus
    If like mentioned in the OP you also got the message to clean the sensor, that would indicate that the safety systems were not working as intended. If you remember the messages be sure to write them down as best as you can remember them along with whatever else you remember acquiring. Many times the messages need to be seen several times before they can be fully comprehended, mostly due to other distractions at the times they show up and/or the amount of time they are visible on screen.
    The Toyota safety systems are very good, but they are not prefect. If you pay close enough attention to the car when there is low traffic volume you may get lucky and see when a sensor detects something and reacts incorrectly. When it happened to me I was very confused about exactly what the sensor(s) had detected.
     
    #7 vvillovv, Dec 21, 2020
    Last edited: Dec 21, 2020
    schja01 and davecook89t like this.
  8. Salamander_King

    Salamander_King Senior Member

    Joined:
    Nov 8, 2015
    7,905
    6,324
    0
    Location:
    New England
    Vehicle:
    2020 Prius Prime
    Model:
    LE
    It must be very rare, but I have read a thread with PCS malfunction very similar to what OP has described. It was by @PiPLosAngeles I believe... His car was PP Plus, so it did not have ICS. IIRC, his incident happened at the intersection very similar to what OP described. But I can't find the thread. I hope he will chime in. I don't remember he commented on any repair or fix. I think he just turned off the PCS after the incident.
     
    #8 Salamander_King, Dec 21, 2020
    Last edited: Dec 21, 2020
  9. hox

    hox Junior Member

    Joined:
    Mar 25, 2009
    15
    10
    0
    Location:
    Portland, OR
    Vehicle:
    Other Non-Hybrid
    To follow up on my OP. I finally had the opportunity to talk Corporate Toyota and they said to take the car to the dealership for a full diagnostic. I purchased the car from Ron Tonkin Toyota in Portland and that is where I dropped it off today. Tech said they could have the car a week or so but they do not offer any loaners, just told me to rent a car. This is the first dealership when a warranty issue prevents the use of my car for > 1 day that a loaner is not offered.
    For this service diagnostic, I asked them to address three issues:

    1. The autonomous braking for no reason done by the car at an intersection. (Described in this post.)
    2. The random rebooting of the system while driving. Tech blamed this on Apple stating that Apple refuses to provide code that would allow Toyota to modify its software to prevent the random rebooting of its computer. Tech recommended deleting my iphone from the hand-free setup to prevent this issue.
    Barely believable solution.

    3. The constant collision error coming from the front right sensor. This goes off every time the car rolls to a stop. I have cleaned all the sensors with a microfiber towel, which did not fix this issue.

    So here is the only way I can drive the car without issues 2 and 3: turn off all the collision sensors, turn off lane departure, delete Iphone from my bluetooth setup on the car.

    I will share what I find out regarding the autonomous braking error.
     
    #9 hox, Jan 9, 2021
    Last edited: Jan 9, 2021
  10. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    91,713
    41,352
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    they'll probably charge you if they can't find anything
     
    Mendel Leisk likes this.
  11. Mendel Leisk

    Mendel Leisk Senior Member

    Joined:
    Oct 17, 2010
    42,893
    30,688
    80
    Location:
    Greater Vancouver, British Columbia, Canada
    Vehicle:
    2010 Prius
    Model:
    Touring
    This thread’s title could be more succinct? OP’s call, but every time I read it I’m scratching my head. Mods can revise if you “report” it.
     
  12. Tideland Prius

    Tideland Prius Moderator of the North
    Staff Member

    Joined:
    Oct 2, 2004
    42,212
    13,761
    41
    Location:
    Canada
    Vehicle:
    2018 Prius Prime
    Model:
    Technology
    @hox I made the change to the title to something more descriptive.
     
    schja01 and Mendel Leisk like this.
  13. Gokhan

    Gokhan Senior Member

    Joined:
    Oct 5, 2008
    1,003
    467
    0
    Location:
    Paramount CA
    Vehicle:
    2021 Prius Prime
    Model:
    Limited
    As you said the system probably braked for a small animal that the driver failed to see and otherwise would hit it. Since it happened only once, I wouldn't worry about it.

    Moreover, people behind you are not supposed to follow you so close that they can't stop if you suddenly apply the brakes. If they hit you, they would be 100% at fault regardless of why and how you braked.

    How Do You Prove Liability for a Vehicle Accident? | Nolo.

    "If someone hits you from behind, it is virtually never your fault, regardless of why you stopped."
     
    #13 Gokhan, Jan 10, 2021
    Last edited: Jan 10, 2021
    Tyfly likes this.
  14. Hicksite

    Hicksite Member

    Joined:
    Apr 22, 2020
    152
    74
    0
    Location:
    Florida
    Vehicle:
    2020 Prius Prime
    Model:
    Limited
    The key word is “virtually”.
     
  15. Hicksite

    Hicksite Member

    Joined:
    Apr 22, 2020
    152
    74
    0
    Location:
    Florida
    Vehicle:
    2020 Prius Prime
    Model:
    Limited
    Not to mention the concept of comparative negligence.
     
  16. Sarge

    Sarge Senior Member

    Joined:
    Nov 28, 2005
    1,011
    428
    0
    Location:
    Milton, Ontario, Canada
    Vehicle:
    2014 Prius Plug-in
    Model:
    Technology
    Sounds to me like this sensor is the issue, and should not be hard for a dealer to confirm/diagnose?

    Aside comment, is it normal/expected that this “clean sensor” message comes up? I haven’t heard this before, but I don’t have a Prime (yet). My Gen 3 PiP has the earlier PCS, and in 5 years of driving this car it has only TWICE beeped very momentarily for a false alarm, but never braked. Once, the shoulder belts began retracting, which was interesting and unexpected. :)

    BTW, I would strongly consider finding another dealer.... not offering a free loaner car for a repair exceeding more than on basic warranty is unacceptable, IMO.... I would fight that.
     
    Tyfly likes this.
  17. fuzzy1

    fuzzy1 Senior Member

    Joined:
    Feb 26, 2009
    14,590
    8,064
    90
    Location:
    Western Washington
    Vehicle:
    2012 Prius
    Model:
    Three
    ... especially when you have just barely started moving from a prior stop and red traffic light.
     
    Gokhan likes this.
  18. pghyndman

    pghyndman Active Member

    Joined:
    Dec 27, 2018
    284
    269
    0
    Location:
    CT shoreline
    Vehicle:
    2021 Prius Prime
    Model:
    Limited
    It might not be a bad idea to investigate and correct the false signal the sensor is producing, as methinks there is a possibility it is tied to the BRAKE issue.
     
  19. hox

    hox Junior Member

    Joined:
    Mar 25, 2009
    15
    10
    0
    Location:
    Portland, OR
    Vehicle:
    Other Non-Hybrid
    Thank you for the thoughts and replies. Thanks for the forum managers for shortening the title.
    Agree on the loaner not offered. To be clear the car is < 1 year old. Full warranty should be in place so I am not expecting any charge for this.

    Regrading the intersection where the autonomous STOP triggered, it is a left turn arrow that lasts 15 seconds. Folks that live in this sub-division know this and are very aggressive to make the light as it does not cycle very frequently, so getting rear ended is a possibility.


    Does it really matter if someone hitting me is at fault? This is a new car and I really don't want to get injured or have an accident on my CarFax associated with this car, let alone having to deal with the unavoidable depreciation tied to damage.

    Regarding what triggered the emergency braking, who knows maybe a mystery sparrow, but nothing that I could see. When this happens though folks need to understand that the car locked up and would not allow me to put the car into drive without turning it off. I was lucky to be in an empty intersection. No steel road plates were in this intersection, I mention this as it seems one in a very busy Seattle thoroughfare triggered an emergency stopping causing everyone behind her to lock up their brakes.

    Automatic braking sometimes brakes for nothing

    I own three Prius cars, so please do not take my posts as being someone who will badmouth the car no matter what. I bought them because of their reliability and will keep this sentiment once this gets sorted.



    Will let you know when I have any information.
     
  20. fuzzy1

    fuzzy1 Senior Member

    Joined:
    Feb 26, 2009
    14,590
    8,064
    90
    Location:
    Western Washington
    Vehicle:
    2012 Prius
    Model:
    Three
    Being worried about the CarFax report, smacks me as allowing the tail to wag the dog.

    If you had been hit, in that situation where you were just starting to move from a previous full stop, then either it would have been a very low speed hit, or it would have been a higher speed strike in which you were destined to be hit regardless.
    That case was a 2010 edition. There should be several rounds of improvements rolled in to your 2020.

    As someone who actually has been hit in a chain reaction crash on a very busy Seattle thoroughfare, in a case that would have been prevented by automatic braking, I'm not going to let perfection be the enemy of improvement.

    With less-than-perfect AEB, you remain undamaged. With less-than-perfect AEB, that linked Seattle driver went undamaged. In the complete absence of AEB, I received minor damage, and the guy behind me received major damage, when the driver behind him on I-5 through Seattle failed to recognize an all-traffic-stopping situation in time.
     
    #20 fuzzy1, Jan 11, 2021
    Last edited: Jan 11, 2021
    Tyfly likes this.
Loading...