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Smart Key not starting car after battery replacement

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Garethh, Apr 29, 2019.

  1. Garethh

    Garethh Junior Member

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    Hi!

    I replaced the battery of my fob with a brand new duracell 2032 with positive side up (i am writing every detail so you don't think i messed it up.). All the buttons on the fob work. The red light is there. I can (un)lock the car without pressing the buttons (smart entry or whatever it's called works.). However, the car won't start unless i put the fob into its slot. I searched the forum and saw that some people solved their same problem by pressing the key button under the steering wheel. My button is unpressed (sks on) as it should be. I checked the 12v battery and it's in perfect shape. What is going on, any ideas?

    Thanks!
     
  2. bisco

    bisco cookie crumbler

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    it stopped working exactly when you changed the battery? could the rfid chip have fallen out?
     
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  3. TMR-JWAP

    TMR-JWAP Senior Member

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    If the car starts only if he inserts the fob into the slot then the RFID is working properly. Is the red light on ONLY when a button is pushed?

    If the key fob appears to be working correctly, with the red light illuminating only when a button is pressed, I would probably try cycling the SKS button under the steering column again. Make sure it's in the out position when done.

    Do you have a backup / second FOB?
     
    #3 TMR-JWAP, Apr 29, 2019
    Last edited: Apr 29, 2019
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  4. Garethh

    Garethh Junior Member

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    yes, exactly after the battery replacement. i am positive nothing has fallen out. I did the whole thing on an empty table, and i was very careful.
     
  5. Garethh

    Garethh Junior Member

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    Yes the red light lights up only when a button is pressed. And I tried cycling the key button. It didn't help. It is in the out position. I do have a second fob that i hadn't used in years. I replaced its battery to try if it works. And that fob is completely gone for some reason. Its red light doesn't even light up even after a brand new battery replacement. I checked for oxidation but nope, clean as a whistle.
     
  6. bisco

    bisco cookie crumbler

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    no idea if it would matter, but try putting the old battery back in
     
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  7. Garethh

    Garethh Junior Member

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    that's actually not the worst idea. however, that battery is looong gone.
     
  8. bisco

    bisco cookie crumbler

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    can you put a volt meter on the new battery?
     
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  9. Garethh

    Garethh Junior Member

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    hmm. my roommate takes the voltmeter to work. I should try that when he gets home.
     
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  10. Garethh

    Garethh Junior Member

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    the battery is good. anyone?
     
  11. TMR-JWAP

    TMR-JWAP Senior Member

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    I've always been told driving a Prius is like driving a computer.

    When something on my computer, an attached device or a network connection doesn't work I usually just reboot it to gain communication again... Maybe your car needs the 12v (-) terminal disconnected for about ten minutes. Let the car totally power down, capacitors and everything. Then connect it and fire up the car and see what happens? Kind of like 'when all else fails..reboot it'

    Also assuming you do not have Techstream software?
     
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  12. Garethh

    Garethh Junior Member

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    Oooooh! This is great! I can buy it on ebay for like $8. I didn't know about this. Thank you!
     
  13. bisco

    bisco cookie crumbler

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    is the battery 3.3 volts?
     
  14. Garethh

    Garethh Junior Member

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  15. bisco

    bisco cookie crumbler

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    that's basically dead. a new one should be 3.3

    when my garage opener stopped working, it was 3.2
     
  16. Garethh

    Garethh Junior Member

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    i'm sorry i am an idiot. voltmeter reading was 3.3v. for some reason, i gave you the number on the package.
     
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  17. Hawks48

    Hawks48 Junior Member

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    Mine did the same (both fobs). The new battery was slightly thinner, and wasn't making a good contact. I had to put some folded paper between the battery and the cover. That worked.
     
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  18. bisco

    bisco cookie crumbler

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    wow, that is interesting!
     
  19. Garethh

    Garethh Junior Member

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    unfortunately, that's not it. it was one of the first things i tried. btw i got my other smart key working and it does the same thing. it's like the car itself lost its programming or something. anyhow have a similar experience at all?
     
  20. bisco

    bisco cookie crumbler

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    check the 12v health