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ICE comes on when Stopped -- yet monitor shows it's OFF

Discussion in 'Prime Main Forum (2017-2022)' started by stevepea, Dec 2, 2017.

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  1. stevepea

    stevepea Senior Member

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    Here's a different ICE problem that has happened to me at least 3 times in the 4,000 miles I've had the car. Please note that this isn't the car's normal behavior, but it's happened a few times now, to where I'm wondering what's going on.

    When the EV range is gone and I'm in HV mode, and I reach a traffic light, sometimes the ICE comes on and/or does not shut off.

    Please note the following:
    (1) The traction battery is NOT low (and needing to be recharged -- that would make sense). Each time this has happened, I've immediately looked, and the icon has been right at the "buffer" line, not below it. (Even when the icon is somewhat below the buffer line, in normal circumstances if you come to a stoplight, the ICE won't come on unless you're really below it). Each time this has happened, while there's no EV range left, the HV buffer has been full.

    (2) Most confusingly, the MFD display shows the ICE off. More specifically, it shows NO action going on whatsoever. (In times where the ICE is on to charge the battery, the MFD will show arrows and movement of the ICE into the battery, showing that it's recharging). Each time this has happened, I'll quickly scroll to the MFD screen showing what's going on with the ICE/Traction battery, and the MFD shows nothing going on -- as if it should be completely stopped (as it should be), yet the ICE is on.

    (3) Each of the 3 times I've noticed has been at night, without a lot of traffic around me (easier to hear/feel your engine when there's no other car around you, I guess), but the SoCal nights have been very moderate (60s) -- no cold weather.

    (4) No heat or A/C on (just lights, and 2 of the 3 times, the radio).

    (5) As I've sat there at the signal with my ICE on, yet my battery's buffer full and the MFD showing the ICE is OFF, for 2 of the 3 times, the ICE did shut off after perhaps a minute (a long time in a situation like this). The 3rd time, the signal was short, so I wound up having to move before the ICE had a chance to (eventually) shut off.

    (6) I'm trying to report this accurately, and if I remember right, it's happened both where the ICE was on (traveling, say 45mph and coming to a red light), as well as where the ICE was OFF when moving (in temporary EV mode for just a short spurt, and coming to the red light, then the ICE came on at the light). Again, the battery icon is pretty quick and accurate, it's not like the buffer was depleted by doing a lot of low-speed driving, it showed right at the buffer line -- and again, the MFD showed that the ICE was OFF when it was on. That's what's strange.

    (7) At least 2 of the 3 times was after a freeway trip (though still at a red light, stopped on a street now), and the other time was simply returning from Target late in the evening (no freeway, and at the first signal after leaving Target).

    This isn't the car's "normal" behavior (normally, of course, the ICE is off at a red light). But I've only driven the car 4,000 miles so far, and it's been at least 3 times now where, when stopped at a signal, the ICE is on even though the traction battery icon has shown full buffer -- and even though the MFD is showing that the ICE is OFF. For the 2 times where I was stopped long enough (at a long light), the ICE eventually did shut off, but it took quite a while, perhaps 45 seconds to a minute, when it shouldn't even be on in the first place (temp in the 60s, nothing else in the car being used)...
     
    #1 stevepea, Dec 2, 2017
  2. bisco

    bisco cookie crumbler

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    could it be trying to maintain minimum engine temp?
     
    #2 bisco, Dec 2, 2017
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  3. Data Daedalus

    Data Daedalus Senior Member

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    My Gen 2 Prius does this, particularly when I’ve got a full HV battery pack and the ICE is still cold (more noticeable in cold weather).

    I believe, as Bisco pointed out, that the vehicle’s ECU is trying to get the ICE to optimal temps, utilising the HV pack, and keeping emissions low, by not using petrol at all - something all Prii are.....um.....Primed to do, if you’ll pardon the pun.

    This behaviour is up there with the Gen 2 zooming down a long hill at well over 50 mph and the ICE while spinning, not using fuel for a while. I see this on my commute in the same area almost everyday - but being light footed and exploiting the vehicle’s downhill momentum also contributes to this example.

    I’ve also just started my Prius, wafted to the electric gates at work before the ICE kicks in, and watched as almost immediately, while the gates slowly swing open and I stand stationary, how the ICE continues spinning while using NO fuel - the HV battery is spinning the ICE, till I apply some thrust, then seamlessly, fuel starts to flow on the MFD.

    I would suspect this is perfectly normal, but will differ in exact circumstances, due to the different driving styles and / or road and climatic conditions for each individual Prius - I hope you like my prime examples


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    #3 Data Daedalus, Dec 2, 2017
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  4. Andyprius1

    Andyprius1 Senior Member

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    It’s normal, don’t worry about it. When the engine is really on then the MFD will display it. I f you still have doubts, tromp on the accelerator when the light changes, Now the screen shows engine running, right?
     
    #4 Andyprius1, Dec 2, 2017
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  5. bisco

    bisco cookie crumbler

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    the car screens are not as accurate as a scan gauge.
     
    #5 bisco, Dec 2, 2017
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  6. Andyprius1

    Andyprius1 Senior Member

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    so,...the scan gauge shows what? the engine running?
     
    #6 Andyprius1, Dec 2, 2017
  7. bisco

    bisco cookie crumbler

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    it shows rpm in real time, no delay like dash idiot screen.
     
    #7 bisco, Dec 2, 2017
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  8. Trollbait

    Trollbait It's a D&D thing

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    That would also include the catalytic converter in terms of warming.

    between the numerous data displays, it would be possible to tell if the engine is running or simply spinning without burning fuel.
     
    #8 Trollbait, Dec 3, 2017
  9. Mendel Leisk

    Mendel Leisk Senior Member

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    ScanGauge has a slight delay, maybe a second. On our 2010 (fwiw) it can show RPM when the car's showing no gas consumption. I'm not sure if this is true, ie: the engine is turning over but no gas being used. This'll happen during foot-off-gas coasting at highway speeds, where the engine has to run (again, 3rd gen hatchback), above 73~74 km/hr.
     
    #9 Mendel Leisk, Dec 3, 2017
  10. john1701a

    john1701a Prius Guru

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    Sorry, I didn't even bother to read through the detail... though, it is very much appreciated... since it is necessary to point this out:

    PRIUS WILL RUN THE ENGINE JUST FOR THE SAKE OF CLEANSING EMISSIONS.

    In other words, no matter what you think should happen, it may simply be do for a "housekeeping" cycle. Collected emissions in the trap need to be purged and heat is required to do that. So, the engine runs. This is why Prius is greener than some other vehicles. it is an operation of the system often overlooked... and is quite confusing when it happens for no apparent reason.
     
    #10 john1701a, Dec 3, 2017
    Last edited: Dec 3, 2017
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  11. stevepea

    stevepea Senior Member

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    Thanks for the suggestions on why this might be happening. It is a bit strange though, that when it happens, the MFD still shows nothing happening when the ICE is on in this instance (as it will show the ICE being on in other circumstances where the ICE is on). I know the gauges aren't perfect, but the fact that the MFD is showing that everything's off while the ICE is actually on, more than anything else, is the thing that makes it seem like "it's not supposed to happen."

    Anyway, just wanted to report that this has happened at least 3 times now (perhaps more... the times I've noticed it have been late at night when there's no noise or other cars next to me at the stoplight, and it's real easy to feel & hear that the ICE is on. Maybe it happens more, but during the day with all the cars and other noise I don't even realize it). Again, it's not the car's usual behavior, but it has happened a few times now, with the battery icon showing a full (non-EV) buffer, mild temps, nothing in the car "on" that would need the extra power. Just one of those things, I guess.
     
    #11 stevepea, Dec 4, 2017
  12. bisco

    bisco cookie crumbler

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    it could be a defect, but getting a dealer to diagnose without codes is impossible.
     
    #12 bisco, Dec 4, 2017
  13. stevepea

    stevepea Senior Member

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    I'll see how often it continues. If it's just an occasional thing I'll let it pass, if it seems to happen with more frequency though, I'll ask them to look into it.

    (Hmm.. just remembered an old joke I heard once: "Radio Men do with Frequency. 'Til it Hz).
     
    #13 stevepea, Dec 4, 2017
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  14. bisco

    bisco cookie crumbler

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    we have an owner whose engine always comes on when it's under 50 degrees. maybe you've seen the thread. anyway, the dealer has been useless.
     
    #14 bisco, Dec 4, 2017
  15. RickyV12

    RickyV12 Junior Member

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    Hi Stevepea or other people,
    I got a high mileage beat up 2007 prius, I replaced a used battery and it works fine.
    weather is getting cold at 50F now, I see exactly your problem that ICE is still running.
    After Enginee warm up.
    MFD screen show that ICE is not running.
    While Enery screen show ICE is using fuel.
    ICE do not stop at stop sign.
    I am not sure that it is problem that weather issure or I should unplug 12V car battery so ICE will re-calibrate itself for low emission for colder weather. Yes, I have mild 50% bottom gill block to increase warm up..
     
    #15 RickyV12, Oct 8, 2019
  16. bisco

    bisco cookie crumbler

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    i have read about this problem before, but i can't remember if there was a solution. you're probably gonna need tech stream diagnostic software to figure out what's wrong.

    in the meantime, you should start a ne thread in the appropriate gen 2 forum. this is the prime forum, and steves problem is completely different from yours, even though there are similarities.

    all the best!(y)
     
    #16 bisco, Oct 8, 2019
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  17. Mendel Leisk

    Mendel Leisk Senior Member

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    Definitely don't block the bottom more than 50%: on second gen the inverter radiator is behind there. Block the upper more.
     
    #17 Mendel Leisk, Oct 8, 2019
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  18. vvillovv

    vvillovv Senior Member

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    I'll add that
    I use grille block. In another thread I posted that I'm not confident that the dynamic shutters are active in our Prime,
    I'd recommend when using grille block, it's wise to monitor coolant temps for at least the first year of use. Being able to see when you want to block and how much you want to block is much safer than eyeballing it. ymmv
     
    #18 vvillovv, Oct 9, 2019
    Last edited: Oct 9, 2019
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  19. m8547

    m8547 Senior Member

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    It's just idling the engine, letting it spin with no load. It's not charging the battery or driving the wheels, so the screen won't show it.
     
    #19 m8547, Oct 9, 2019
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  20. Data Daedalus

    Data Daedalus Senior Member

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    My 2008 Prius does that regularly in colder weather or when my HV battery is fully charged and I’ve just started the engine a very short time before.

    Example: waiting for the electronic gates at work to open. I am stopped, immobile, but the engine continues to run, being entirely spun by the full battery to reduce emissions while trying to get the engine warmed to optimal capacity.

    This is perfectly normal.

    It also shows just how sophisticated the ECU programming on the Prius is


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    #20 Data Daedalus, Oct 9, 2019
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