Oddball series of error messages on cold morning

Discussion in 'Prime Main Forum (2017-Current)' started by John roden, Nov 5, 2021.

  1. John roden

    John roden Junior Member

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    2021 was parked last night in damp weather right around freezing and then overnight it dropped down into the mid-20s and froze everything.

    This morning it was about 28 and even after repeated plugging and unplugging the switch on the charge door was indicating that the charge door was still open when it was not. Car was also throwing an error for a low 12 volt battery which seemed dubious given that it is relatively new with 6,000 miles. After a half hour all of the problems seem to resolve themselves.

    Just a fluke?
     
  2. John roden

    John roden Junior Member

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    Also can I pull those codes with a regular inexpensive code scanner?
     
  3. schja01

    schja01 One of very few in Chicagoland

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    Low 12v batteries is the scourge of high tech Toyota hybrids. The charge door has a solenoid so it could be affected. Charge up the 12v battery. If you drive infrequently invest in a tender/maintainer. Keep your FOB away from the car when not in use.
     
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  4. John roden

    John roden Junior Member

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    The car gets a lot of short trips that might not run the internal combustion engine and is plugged in every night. I'm guessing that the propulsion battery is separate from the 12 volt battery? And as a result that 12 volt battery is only charged off the engine alternator which is not being run very much, am I correcting? I can throw it on a charger or tender from time to time to keep that battery topped up if that is the case.
     
  5. Gokhan

    Gokhan Senior Member

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    It sounds like you aren't charging your HV battery and not using the EV mode much, which is draining your 12 V battery (called auxiliary battery by Toyota) too quickly. I believe the HV mode isn't as efficient in charging the 12 V battery as the EV mode.

    If you have a garage, charge your HV battery and leave the car on in READY mode for an hour with the A/C turned off. This will recharge the 12 V battery. Don't forget to go back and turn off the car.
     
  6. John roden

    John roden Junior Member

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    So when you say 12 volt battery I'm assuming that means the little conventional car battery under the hood on the driver side? The car is driven in EV mode a lot for short trips as my daughter drives it to high school and back and to work so I would not be surprised if the internal combustion engine does not run for days on end. It gets plugged in to charge every night.

    If I understand what you're saying I don't have to mess around dragging the battery charger out there instead I can put it in ready, shut off climate control, leave it plugged into shore power and let the big inverter charge up that little battery? Am I getting that right?
     
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  7. Gokhan

    Gokhan Senior Member

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    That's correct. There is a DC–DC converter (not a DC–AC inverter) that charges the 12 V battery (sealed glass mat lead–acid battery) from the lithium-ion HV battery. It only works when the car is in the READY mode.

    Do not leave the charger cable plugged in after the charging is complete. That drains the 12 V battery. Perhaps, this is the problem. Sitting in the car with the lights or accessories on can also drain it. I don't turn off the READY mode until I'm ready to leave the car.
     
  8. Trollbait

    Trollbait It's a D&D thing

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    It charges off the traction battery, but short trips may not provide enough time to charge the battery back up after performing its start up duties. Then when plugged in, there is a draw on the 12V to monitor and run the connection.

    You could leave the car in Ready to charge the 12V. There just isn't a built in way of monitoring the battery's charge level; it has an alert for low charge, but nothing for full. So you'd have to pop the hood and use a voltmeter. If you have a charger already, just use that.

    Like everything else, a 12V can have a defect from the factory. Wouldn't hurt to have it tested to ensure it doesn't have a bad cell.
     
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  9. vvillovv

    vvillovv Senior Member

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    Most likely
    Battery below 12 volts happened to me during a cold snap in the Adirondacks around this time of the season 2 years ago, I took 12 volt reading for a month or two after that to learn more about how 12 volt charging system worked.

    It always depends on what scanner you use as to what hybrid specific codes you'll get from it.
    Torque. Hybrid Assistant and DrPrius apps when paired with an OBD2 bluetooth adapter, can all pull some of the hybrid specific codes. Techstream gets everything, or almost everything the dealers can get.

    From your description, I'd think it's unlikely there will be DTC's stored. In the off chance there were DTC and or freeze data stored in the ECU, it most likely would take techstream or another expensive professional diagnostic tool to get at it.
     
    #9 vvillovv, Nov 6, 2021
    Last edited: Nov 6, 2021
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  10. jerrymildred

    jerrymildred Senior Member

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    Wow. Quite a few misapprehensions. I don't want to be pedantic, but these things will really confuse others who come across them later, so me clarify a bit if I may.
    Then you had a low 12V battery at the time. It's a warning that you shouldn't ignore. My wife ignored it one too many times and I had to go rescue her.

    Hardly any of the scanners sold in parts stores can read all the computers in a Prius. Post #9 by @vvillovv offers some good options. There are many threads here on PC about bluetoooth/wifi scanners and phone apps. They aren't as sophisticates as Techstream, but are good enough most of the time. But in this case, I really doubt if you have any trouble codes.

    Actually, it's just a spring loaded pin under a rubber boot. Works just like the stereo cabinet doors that you push and they pop open but it activates a switch that monitors its position. So, yes, they can get gummy in cold weather, I suppose. But that would most likely lead to the door not popping open. The switch not knowing the door is closed might take some investigation of the visual variety.

    There is no alternator on any Prius. And that's exactly why there is no alternator; the engine rarely runs. If it depended on an alternator, the streets would be littered with Prii needing jumpstarts. Or more likely, Toyota would have only sold a handful of them once word got out how incredibly inconvenient they were. LOL! Therefore, the car has a DC/DC converter as part of the inverter that converts the high voltage from the traction battery to 13-14 volts to keep the 12V charged and it doesn't give a rip if the smog generator is running or not.

    They are exactly the same on my Prime according the the meter I keep plugged in and there is nothing I can conceive of that would make them different because of the above statement that the ICE has nothing to do with charging the 12V.

    I and many others often go for several weeks of daily driving without the ICE running. Makes no difference. Some people report going over a year without buying gas. Remove the "EV mode" qualifier because it's irrelevant and there you have the reason for the low 12V. Short trips. Modern high tech cars have a lot of parasitic drain on the 12V system when they are "off." Repeated trips too short to replenish the 12V will gradually ratchet the voltage down to the point where you get the low 12V message.

    Correct, except the Gen 4 and Prime have regular wet lead acid batteries. This is a change from the AGM in previous generations and is enabled by the much smaller inverter and other components under the hood finally making room for the battery up there.
     
    #10 jerrymildred, Nov 6, 2021
    Last edited: Nov 6, 2021
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  11. John roden

    John roden Junior Member

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    Thank you for taking the time to write this it has helped me understand the car better. I put it on a charger yesterday morning and it came up to 13.1 pretty quickly. I will monitor the battery voltage this winter and use that charging procedure from the traction battery as required.

    I have not owned a new car in ages and the technology on this Prius is just remarkable.
     
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  12. jerrymildred

    jerrymildred Senior Member

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    Indeed it is. I always recommend that new owners of Primes (and even the regular Gen 4) spend some quality time with the owners manual. It'll lead to much more enjoyment from the amazing but sometimes quirky car.
     
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  13. Gokhan

    Gokhan Senior Member

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    In the new-car features manual, it says that the 12 V battery has temperature, current, and voltage sensors attached to the negative terminal. The charging voltage is controlled according to the battery condition and temperature. However, it is not controlled when the temperature is too low or too high, and a constant charging voltage is applied instead.

    FAIL-SAFE

    (a) The hybrid vehicle control ECU stops charging control and the DC-DC converter switches to the constant voltage control mode under the following conditions:

    CONDITIONS: INTENTION

    * When auxiliary battery capacity has decreased, * When auxiliary battery temperature is low or high: When the condition of the auxiliary battery is bad, charging control is suspended to prevent a decrease in auxiliary battery charge. If the auxiliary battery temperature is too low or too high, the auxiliary battery capacity and lifespan may decrease.

    * When the vehicle cooling system load is high, * When the engine load is high: To avoid discomfort caused by voltage fluctuations in the power supply (maintain saleability and provide stable power)

    * When a battery sensor (battery state sensor assembly) is malfunctioning, * When voltage sensing is abnormal: When there is a sensor malfunction, charging control is suspended to prevent a decrease in auxiliary battery charge.

    CONDITIONS: INTENTION

    * When there is a LIN communication error between the hybrid vehicle control ECU and battery sensor (battery state sensor assembly): When there is a LIN communication error between the hybrid vehicle control ECU and battery sensor (battery state sensor assembly), charging control is suspended to prevent a decrease in auxiliary battery charge.
     
  14. Gokhan

    Gokhan Senior Member

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  15. John roden

    John roden Junior Member

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    So this morning was not overly cold at about 40°. I unplugged the car as it had been plugged in all night for the traction battery and it's fully charged. I depressed the brake and pushed the the start button so I can warm the thing up a bit for my daughter while I walked the dog. I hit the defroster and defogger and was surprised that the internal combustion engine fired up.

    Any idea why?
     
  16. Gokhan

    Gokhan Senior Member

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    This is standard operation for Prius Prime—nothing unusual. It is done probably not to overload the electrical system, as it is a plug-in hybrid electric vehicle (PHEV) with good—albeit somewhat limited—EV capabilities.
     
    #16 Gokhan, Nov 8, 2021
    Last edited: Nov 8, 2021
  17. dig4dirt

    dig4dirt MoonGlow

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    That is why.
    If you use the front window defroster button, it will start the ICE engine.
    If you do not want this to happen, you can just use the on screen window/floor vent in heat mode.
    Once you hit the button on left side of the bezel, it will fire ICE up.

    Primes in the northeast are experiencing this since the dip in temp.
    Once you hit 14F ICE will auto startup. May happen for various reasons besides that.
    Observed speculation is that model year 2021 may have had a few slight changes.
    I have a 21 Prime and so far no ICE startup in EV mode EXCEPT for front window defroster once .....
    so I had to give the misses a run down on how to use heat or defog windshield unless icy/cold.

    No EV at startup? | PriusChat

    This is an ongoing thread that is recent
     
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  18. vvillovv

    vvillovv Senior Member

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    Looks like that might be the case, especially around the freezing mark, maybe the 37 degree mark. Might also have some high temp changes as well, but those would probably be less noticeable for anyone not living in the southwest or similar.
     
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  19. Trollbait

    Trollbait It's a D&D thing

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    The heat pump can cool and dehumidify, as that is done at the same coil in the dash. This is just like a plain air conditioner.

    When heating, it can only do a little bit of dehumidifying, as the Prime system does have a second, smaller coil in the dash. The other coil can't dehumidify while heating. This is why manually directing the venting to windows can help with frost and fogging. It might not be enough with heavy fogging.

    Pushing the front defogger button tells the system you want heat and full dehumidifying. That is the quickest way to get fog off the inside of the windshield. So the heat pump goes into cooling mode to dehumidify, and the engine comes on for heat. It might also be the fastest way to defrost, as the heat pump gets less efficient at heating the colder outside it gets.
     
  20. Mendel Leisk

    Mendel Leisk Sand Pounder

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    Yeah, the Prius monitors your heating/venting demands, weighs that when deciding whether or not to have the engine running. Even with my lowly 2010: if I've driven a few blocks, engine still warming up, I might stop at a red light, with H/V set to warm the cabin, and the engine will keep running. If I tick the cabin temp setting down a few degrees, or turn the system right off, the engine promptly stops. Reverse those actions, the engine will start up again.
     
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