Prevent ICE starting in cold weather

Discussion in 'Gen 5 Prius Main Forum' started by Nick Abbot, Dec 18, 2025 at 2:41 PM.

  1. Nick Abbot

    Nick Abbot Junior Member

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    I have a 2024 Prius Prime. Is there any way to prevent the ICE starting up in cold weather?

    I've noticed when the weather/battery is cold, the engine will start while in electric mode, presumably to warm the battery. This the exact opposite of what I wanted this car for.

    I would love to know of any way to prevent the engine from running when the battery is cold.

    My commute is about1500 feet. In cold weather the engine starts about 100 feet from my driveway.
     
  2. Gorgonzola

    Gorgonzola Junior Member

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    One solution might be to bundle up and walk the 1,500 feet. I’m not an owner of the plug-in but I suspect those systems are automated based on the car’s diagnostics and not something you can override.
     
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  3. Mendel Leisk

    Mendel Leisk MMX GEN III

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    1500 feet is 500 yards: 5 football fields end to end.
     
  4. fuzzy1

    fuzzy1 Senior Member

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    At what temperatures are you seeing this? What fraction of mornings is it cold enough to force this mode?

    I haven't had my related '24 RAV Prime out in much serious cold yet (missed most of last ski season due to injury), so haven't learned all its temperature thresholds. While traveling, only once has it been started in cold enough conditions to immediately bypass EV mode and go straight to HV, probably +4F that morning (?). On several morning in the teens, I needed the front defrost to melt off the windshield before moving, also forcing the ICE on. But garaged at home in a milder coastal climate, haven't yet dealt with unwanted ICE operation, it doesn't get cold enough here every winter.

    I also haven't yet run into a "100 feet from the driveway" threshold in this RAV. In my previous Gen3 Prii non-plug-in, that threshold (actually, 10-15 seconds from start) was 68F.
     
    #4 fuzzy1, Dec 19, 2025 at 8:59 AM
    Last edited: Dec 19, 2025 at 9:47 AM
  5. ChapmanF

    ChapmanF Senior Member

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    excluding end zones
     
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  6. VelvetFoot

    VelvetFoot Active Member

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    Canadian Football?
     
  7. AgentPTFC

    AgentPTFC Member

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    what are your climate settings? the max defog will force the ICE to to come on.
     
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  8. BiomedO1

    BiomedO1 Senior Member

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    There's a bunch of things that will trigger the ICE; most of which is designed to protect the overall system. Overriding it will likely cause damage, over the long run and reduce reliability. Toyota engineers did a fairly decent job of protecting the overall system.


    PS; keep an eye on your 12V aux. battery level. Those short hops, you'll be running at a deficit and slowly draw down that battery - not enough time to recharge/recoup-orate.
     
    #8 BiomedO1, Dec 19, 2025 at 11:51 AM
    Last edited: Dec 19, 2025 at 2:32 PM
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  9. bisco

    bisco cookie crumbler

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    trade it in for a bev, the engine never comes on
     
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  10. PriusCamper

    PriusCamper Senior Member

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    Easy... Just need to install an engine block heater and set it up so if you forget to unplug when you drive off in a rush it unplugs itself.
     
  11. Nick Abbot

    Nick Abbot Junior Member

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    The climate settings were zero - none. Also, no steering wheel heater or seat heater.
     
  12. Nick Abbot

    Nick Abbot Junior Member

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    I appears I've under estimated level of maieutics here. The road between my home and work is winding and mostly has 1.5 inches between the fog line and a ditch - not much walking room - it's also a steep hill.

    I guess I'll just have to remove the sparkplugs and disconnect the fuel injectors in the parking lot before I drive home.
     
  13. BiomedO1

    BiomedO1 Senior Member

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    Your probably joking, but if your not - just disconnect the ignition coils. Expect a check engine lamp.
     
  14. Nick Abbot

    Nick Abbot Junior Member

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    I find it fascinating how you assumed I was leaving my home when in fact I was referring to the opposite. Going to work my battery is warm - the car started out in my heated garage. But after being at work for 4 hours in 10F-15F degree weather, the battery is cold enough for the ICE to start about 100' from my house as I go home for lunch. I guess for the first 1400' of my drive home, the computer is pondering life's other more important mysteries - perhaps like, "why do so many people answer simple direct questions with more questions?"
     
  15. Nick Abbot

    Nick Abbot Junior Member

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    Yes, of course it's a joke. the car is still under warranty - I'm not touching anything.
     
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  16. mva

    mva Member

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    If you’re going down a steep hill with a pretty full, and cold, EV battery the ICE will start. I have had this happen many times.

    The solution for me is to be very gentle on the brake pedal or switch the car into neutral on the steep part of the downhill.
     
  17. fuzzy1

    fuzzy1 Senior Member

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    Simple questions often lack sufficient case detail to properly answer more complex problems. Necessary or relevant variables are still unknowns, leaving the matter under-defined.

    Snooty slapbacks are not a productive path towards pinning down those unknowns.