Smart Key/Keyless issue: works randomly, different handles respond, someting

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Kamilpcc, Aug 11, 2025 at 8:52 AM.

  1. Kamilpcc

    Kamilpcc New Member

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    I’m having an issue with the Smart Key/Keyless system in my Gen 2 Prius and I’m wondering if anyone has experienced something similar.

    Symptoms:

    The car starts fine with both keys (both when inserted and without inserting – the transponder is recognized).

    The problem is with locking/unlocking the doors using the handle (keyless) and sometimes with the remote buttons.

    The LED on the key fob blinks when trying to lock, but the car doesn’t lock.

    Sometimes the driver’s door handle works, sometimes only the left rear door handle works, and sometimes neither.

    Sometimes the trunk button will lock/unlock, and then it stops working again.

    Sometimes the keyless works perfectly in the morning, but after a few hours of parking or even after a short drive it starts acting up.

    Occasionally, the handle button only works if the fob is close to the rear antenna (near the rear door), but not from the front.

    On the dash, I sometimes see the orange “car with a key inside” indicator (not the golden immobilizer one) blinking.
     
  2. JC91006

    JC91006 Senior Member

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    Have you tried changing the battery in your FOB?
     
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  3. Kamilpcc

    Kamilpcc New Member

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    I've replaced the batteries, but that didn't help. It just works randomly, or sometimes it detects the key inside and I have to insert it into the drawer. Sometimes I don't even know what's going on.
     
  4. Kamilpcc

    Kamilpcc New Member

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    One more thing, what does the AGM battery have to do with this? I'm looking, and I don't know where to look. Why did the antennas suddenly fail? Apparently, they're in the door handles. And suddenly everything worked, and it got worse and worse. I was curious about the AGM's voltage. It's 12V. When I turn on the ignition, it drops to 11V, and then to 10.6V after a while when I turn on the lights and blower. But even if I turn on the ignition and charge the battery, it doesn't change the operation of the SKS (keyless) system. The best part is that when I press the button on the door handle, the LED in the remote flashes, meaning they're communicating, but the car isn't following the command, or the remote isn't sending this information to the car. I don't know what I'm talking about anymore.
     
  5. Tombukt2

    Tombukt2 Senior Member

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    Do you have the troubleshooting section for the manual it's almost one complete book? A guy posted in another similar thread you should try n get it . Looks like complete manual set online . You will need it it is extensive paper and pen. Is a must.
     
  6. bisco

    bisco cookie crumbler

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    get a 12v load test
     
  7. Kamilpcc

    Kamilpcc New Member

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    Unfortunately, I don't have such instructions
     
  8. Kamilpcc

    Kamilpcc New Member

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    Czy możesz mi wyjaśnić co masz na myśli i jak to zrobić???
     
  9. Kamilpcc

    Kamilpcc New Member

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    And now the best part. This morning, I started the car without any problems. I live in a housing estate. I went into the menu, the AGM voltage was 11.7V, and I drove to work. I have clean air at work, no buildings, and absolutely no problems.
     
  10. Kamilpcc

    Kamilpcc New Member

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    It's already been revealed what's going on. I've replaced the AGM with a regular Bosch S4 lead-acid battery. I wonder if my fuel consumption will improve if I install the AGM, as many people have written that the AGM has a huge impact on fuel consumption.
     
  11. dolj

    dolj Senior Member

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    As long as the battery is in good condition, it will make no difference.

    The Bosh S4 is a regular flooded lead/acid battery. It probably will not last as long as an AGM.

    There are advantages to the AGM chemistry, but better fuel economy is not one of them.

    You may experience a negative impact on fuel economy if any battery (flooded or AGM) has a shorted cell or similar issue.
     
  12. Kamilpcc

    Kamilpcc New Member

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    Okay, I understand. Well, it's dropping to 10.9V, so that's not good. My question is, is fuel consumption of 5.2-5.3 liters of gasoline okay, mainly in the city and on short trips? Do I need to work on my technique? And why is it that after driving during the day, my battery is almost empty according to the MFD screen, but when I drive to work the next morning, it's either below 50% or even at the limit? Does this mean my HV battery needs checking?
     
  13. Kamilpcc

    Kamilpcc New Member

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    and could this be the reason why my keyless system is malfunctioning?
     
  14. dolj

    dolj Senior Member

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    No, that is not good. Have you charged this battery up? If not, then I would advise you to do that then test the battery. I understand this is a new battery, but it is not giving the results you would expect from a new battery, so you need to ensure the 12 V battery is healthy, otherwise you could end up chasing your tail.
    It's not awful given the city and short trips. There are so many things that can affect fuel economy, so it is hard to say what you might do to improve your numbers. If you could get 4.7 L/100km, you would be happy with that.
    Hard to say, but it does not necessarily mean you have HV (hybrid vehicle) battery is having problems. If you haven't done any battery reconditioning, that might be something that you could look into.
     
  15. Tombukt2

    Tombukt2 Senior Member

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    Gas mileage issues make sure nothing dragging top of small hill neutral the car should fly down hill like soap box derby car . Google it . You should hear no scraping dragging but the wind is down we're trying to hear stuff slowing us. If hi mileage HV battery wen ya change you will notice mpg changes you mite not see 55mpg . Just remember you're driving a 20-year-old gas saver reg cars are catching up in mpg. You still getting better mpg than most for like 2500 bucks. They makin payments