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Strange problem

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Dominic&Leslie, Dec 11, 2020.

  1. Dominic&Leslie

    Dominic&Leslie Junior Member

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    Vehicle:
    2012 Prius
    Model:
    Four
    My day started bad, got into my prius and I noticed the dreaded "check hybrid system" the car drove fine though. I even used the EV mode coming home, yet the light stayed on. So I disconnected the battery.
    Afterwards the check hybrid sysyem light went out but I noticed a new problem, seems when I turn the car off, the brake lights (or the back lights) remain on.
    Sometimes when i turn the car off, everything shuts off just fine, but after 5 minutes or so, the back lights do come back on.
    It is frustrating to say the least and its coming down to, keep the engine running while its parked, or disconnect the car battery, and for now I started to do the battery routine. The 12v battery is less than a year old, plus i drove the car a few hundred miles yesterday because we are in the process of moving.

    I assume my hybrid battery is on its way out soon, but I have no idea whats going on with the back lights. Has anyone ever heard of this happening, or do you have any suggestions?
     
    #1 Dominic&Leslie, Dec 11, 2020
  2. Grit

    Grit Senior Member

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    Four
    Check what the CEL suggests.
     
    #2 Grit, Dec 11, 2020
    pjksr02 and SFO like this.
  3. tankyuong

    tankyuong Senior Member

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    And check the 12v battery
     
    #3 tankyuong, Dec 11, 2020
  4. fotomoto

    fotomoto Senior Member

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    It could also be a mechanical issue with the brake pedal and brake light switch losing the physical connection between the two when at rest. The pedal could be settling enough to activate the switch. The switch is adjustable and could be sticking.

    When the lights come back on, pull the brake pedal up with your hands and see if the lights go off.

    Regardless, you've got bigger fish to fry with the HV system. Older Gen 3 owners near or out of battery warranty should seriously look into grid-charging maintenance for their packs.

    GOOD LUCK!
     
    #4 fotomoto, Dec 11, 2020
    Pluggo and SFO like this.
  5. Dominic&Leslie

    Dominic&Leslie Junior Member

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    Vehicle:
    2012 Prius
    Model:
    Four
    What is CEL?
     
    #5 Dominic&Leslie, Dec 11, 2020
  6. fotomoto

    fotomoto Senior Member

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    On an automotive forum it's an acronym for Check Engine Light. This means there are OBD codes that can be read by a capable code reader and greatly narrow down the issue.
     
    #6 fotomoto, Dec 11, 2020
  7. davecook89t

    davecook89t Senior Member

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    Four Touring
    Any trouble lights or messages appearing on your dashboard are associated with error codes that need to be read in order to properly diagnose the problems your car has. An auto supply store would be able to read any codes for you that do not originate from the hybrid system. The hybrid system codes could normally only be read by a Toyota dealer or someone with access to a hybrid compatible code reader such as those recommended here.
     
    #7 davecook89t, Dec 11, 2020
  8. pjksr02

    pjksr02 Active Member

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    Location:
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    Vehicle:
    2010 Prius
    Model:
    III
    Are you up-to-date on all the recalls on your car? Did you have the Intelligent Power Module replaced?
     
    #8 pjksr02, Dec 11, 2020
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