2018 Prius in drive, randomly won't move forward. Toyota can't replicate....

Discussion in 'Gen 4 Prius Technical Discussion' started by Jeff Jefferson, Jul 24, 2024.

  1. Jeff Jefferson

    Jeff Jefferson New Member

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    Hey all, wanted to make a post here to see if anyone has run across this issue.

    I have a 2018 Prius that I bought new (in 2018!). I don't drive it a crazy amount, currently has 58,000 miles on it.

    Around August 2021, I had an odd issue. I came to a stop sign and when it was my turn to go, I pushed the accelerator and the car barely moved at all. Like half a foot. The engine revved but the car would not accelerate forward. I managed to pull to the side of the road, put it in park, then back to drive. Still wouldn't move. Turned the car off and back on, then it drove like normal. No error lights came on, no error codes, car always showed in "D". Other than the car not moving, you'd have never known there was an issue.

    Called Toyota dealership and they inspected the car the next day. They had it a full day, ran diagnostics, road tested, could not replicate the issue.

    So I took it home and it was fine until a couple weeks ago (3 years without the same issue!). Same thing happened. I took it into Toyota, they could not replicate. Unlike last time, the problem has now popped up again 2 weeks later.

    This time I did a recording. Again, no error lights of any kind, car stayed in drive but sort of felt like in neutral. THIS time I tried pumping gas pedal, bake pedal, neither did anything. I tried just pushing down on accelerator and it "caught" and felt like it jerked forward/shifted, then it drove forward as usual. Once I came to a stop about 20 yards away, same issue.

    I turned the car off for about 60 seconds, started up, and it worked.

    One thing that kind of stuck out to me is once I started driving AFTER restarting the car, I kind of noticed a loud vent sound in the right rear. This was aside from the AC that was on. Come to find that this cools/vents one of the batteries.

    One other thing of note is that this is in CA and was very hot (100+). However, I've driven the card plenty of times in that type of heat without this issue.

    Anyone have any experience or ideas of what this could be? As I said above, the official Toyota service center never heard of the issue and has been unable to replicate the issue twice. Best way I can simply describe it is it feels like the car is in neutral but it's not in neutral. Kind of frustrating overall but hoping I'm just missing some other explanation. Thanks for any feedback or experiences!
     
    #1 Jeff Jefferson, Jul 24, 2024
  2. FuelMiser

    FuelMiser Senior Member

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    Could be the traction battery under the rear seat is overheating and the drive system is going into limp home mode. Especially since you heard the "vent" sound coming from the rear seat area. I'd tear into the traction battery cooling system (vents, filters) even removing as much of the components covering the traction battery (rear seat, cargo area flooring) as possible and inspect the entire traction battery cooling system you can. Maybe look up "how-to" videos on YouTube.
     
    #2 FuelMiser, Jul 25, 2024
    Brian1954 likes this.
  3. ETC(SS)

    ETC(SS) The OTHER One Percenter.....

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    How many pets in the car?

    You need to do two things:
    1. Stop going to Toyota dealerships. Maybe buy a car from them once in a while, but I lost faith in their dealership service departments a while back.
    2. As mentioned above, see why your traction battery vent fan is competing with your HVAC fan for your attention.

    If it's not hair, it might be heat.
    Park outside a lot?

    I'm surprised that, based on your symptoms they didn't investigate your battery more thoroughly.
     
    #3 ETC(SS), Jul 25, 2024
  4. Jeff Jefferson

    Jeff Jefferson New Member

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    Thank you both for response. I don't have any pets but car is always parked outside, and it's always hot out.

    When I first took it to Toyota 3 years ago, the service tech (prior to looking at the car/testing it) opined that it was likely a battery issue but after looking at it they said the batteries were fine (not sure exactly what they did to confirm). The only plus side of these 2 costs is they charged me nothing since they found no problems.

    I'll poke around some on the traction suggestion. Just really confusing to me that the problem disappears for three years and here it is again. Anyhow, thanks again for input
     
    #4 Jeff Jefferson, Jul 25, 2024
  5. Mr.Vanvandenburg

    Mr.Vanvandenburg Senior Member

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    Difficult to diagnose intermittent problems. I always go for the obvious, the 12 volt battery is acting up? How old is it? Or the throttle drive by wire control is acting up? I don’t know where it is on your car, near the gas pedal under the dash I guess. Or the throttle body side of the drive by wire system. Seems like a logical area to start with. Could the sensor be loose? I only played with a 2002 Camry system. I think it just requires a multimeter and the service manual to check.
     
    #5 Mr.Vanvandenburg, Jul 25, 2024
  6. Jeff Jefferson

    Jeff Jefferson New Member

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    Happened again today after a couple days of no issues. What I clearly noticed is that back vent did NOT kick on until after it stopped moving.

    So, came to a stop, wouldn't move, pushed gas all the way down in able for it to at least move a little to where I could get it to side of road. At that point that back vent was very audible (unlike prior to that). Whatever the issue is has to somehow be tied to that

    Going to take it to the repair shop down the street (as opposed to Toyota) and see if they've got any ideas. I'll post if it gets resolved, just in case someone else in the future runs into the issue (guessing it's rare).
     
    #6 Jeff Jefferson, Jul 26, 2024
  7. Mendel Leisk

    Mendel Leisk Senior Member

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    Likely there’s some threshold, say battery temp: it’s exceeded only sporadically, and then the software shuts things down, for protection.


    I would do the aforementioned check of hybrid battery fan first.
     
    #7 Mendel Leisk, Jul 27, 2024
  8. vvillovv

    vvillovv Senior Member

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    suggest start documenting details since it's happening often presently. Take pictures and make videos describing what you see, hear, time of day, location address, outside temps and All the A/C setting, what are the cars gauges Showing
    , % SOC of battery
    SOC is High always at or near the top of the gauge.
    SOC is Medium, always near the middle of the gauge.
    SOC is Low, always near the bottom of the gauge

    Always at a Stop Sign? Anything unique about the Stop Sign(s)? Ever at a Stop LIght(s)?

    Start with the basics. Than see if you can start diagnosing and documenting other details. Organize your data on paper, a spreadsheet, picture log (blog), Video log (vlog), whatever is the easiest or least frustrating way for you.

    Once you get your feet wet with the basics you can start looking. listening for more details using other inexpensive tools beside what's already available that came with the Prius.

    Good Luck on your new journey of discovery ... in the Gen 4 Prius Matrix

    Oh yeah, start flipping through the gauge clusters on your middle screens. Don't expect to understand them all, but do start looking at them and focusing on the ones you know what they are showing you.
     
    #8 vvillovv, Jul 28, 2024
    Last edited: Jul 28, 2024
  9. marratj

    marratj New Member

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    #9 marratj, Jul 28, 2024
  10. Lucci

    Lucci New Member

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    Have you had any movement on this issue?

    When this started happening, did you have the standard maintenance reminder?
    I have had the same issue and it seemed to get worse (more frequent) over time. (until) I took it to a dealership and they cleared the maintenance message and told me that nothing was wrong.

    My working theory is that it starts and gets worse when the maintenance message starts and the longer (months) the maintenance message is on. At the time of taking it in I was doing my own basic maintenance and had not cleared the message for over 18 months. during that time it progressively happened more frequently. (once every few months happened once or twice, every other month happened once or twice, then once or twice a month, to several time a month, and finally the last few weeks a few times a week)

    Since taking it into the dealership the issue has not happened again. (going on a couple months now)

    There was a similar issue for the 2022 Prius and Prius Prime that had a recall on the Engine Control Unit (recall number: 21TB07/21TA07)
     
    #10 Lucci, Sep 16, 2024
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