2011 Prius: check hybrid system and check engine light on

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by AdkPrius, Jan 13, 2021.

  1. AdkPrius

    AdkPrius New Member

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    Jan 13, 2021
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    Location:
    Northern NY
    Vehicle:
    2011 Prius
    Model:
    Three
    Long time lurker, first time poster. Please forgive the length.
    I took my 2011 Prius (about 112k miles) to the mechanic to have necessary work done on the front brakes. Left it on a Friday, the mechanic looked at it on Friday and had me leave it over the weekend. On Monday they called me to tell me that the car wouldn't start, saying they took the keys out of the car. [I'm 99.99% sure that they forgot to turn it off, took the keys out of the car, and killed the 12V battery (Optima yellow top, 3 years old, no problems at all with the battery or anything else except the brakes)].
    On Monday they said the alternator was testing fine, but they couldn't get the battery to hold a charge. They called me on Wednesday, told me they were able to trickle charge the battery from a terminal at the fuse box under the hood and everything was fine.
    When I got there to pick it up Wednesday afternoon, the check came on and I got a "check hybrid system" message at start up. They checked the codes, which read something like it could not communicate with the hybrid system. They cleared the codes, it started up normally and I drove it home. No performance issues and the hybrid system appeared to be available (i.e., the gas engine turned off at stops and the car seemed fine).
    Once I got home, the check engine light came on again, and I also got the "check hybrid system" message again. The weirdest thing is that when I turn the car off, the check engine light is dimly illuminated (not as bright as when the car is turned on, but clearly visible), and when I take the key out of the car, I get a "key not detected" message. The heater vents inside the car have hot air (not blowing, but just warm air) even though the car is off and the heater was off when I hit the power off button. I can also hear buzzing sound from under the hood, as if the car is not turning off all the way. For now we have disconnected the 12V battery so that it won't drain overnight while we figure out what to do with it.
    I'm really worried that the mechanic jumped my car improperly and screwed up the hybrid system. Is this even a possibility? If not, what might be wrong and how can I fix it (or insist the mechanic fix it)?
     
  2. rjparker

    rjparker Senior Member

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    Location:
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    Vehicle:
    2012 Prius v wagon
    Model:
    Three
    I doubt serious hybrid damage was done if you drove it home and the engine was cycling as expected. I would suspect the 12v battery could be bad due to a light being left on and they managed to get a little charge on it.

    The car has no alternator. The inverter converter charges the 12v battery. If you have a voltmeter and know how to use it, measure the 12v. It needs to be at least 12.0 v and ideally 12.7 v with the Prius off. If not or if you can not measure it, I would get the existing battery load tested at a dealer or auto supply. It may need a new battery.
     
  3. AdkPrius

    AdkPrius New Member

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    Location:
    Northern NY
    Vehicle:
    2011 Prius
    Model:
    Three
    Thank you so much, rjparker - I appreciate your reply.
    As I mentioned, we disconnected the 12V last night; when we reconnected it this morning, after the *second* start-up, no maintenance lights are on, I'm not getting any messages, and the gas engine cycles on and off and the hybrid battery is showing fully charged. Much to my relief!
    I will take it for a drive later today and make sure it's functioning normally but so far today it seems much, much better. I'll also have the battery load tested ASAP. If it keeps acting up I'm going to push for the mechanic to purchase me a new 12V battery.
     
  4. rjparker

    rjparker Senior Member

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    Location:
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    2012 Prius v wagon
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    Three
    Sounds like a plan.
     
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