Won't start with good 12V battery

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Belliott, Aug 28, 2025 at 12:01 PM.

Page 2 of 2
  1. ChapmanF

    ChapmanF Senior Member

    Joined:
    Mar 30, 2008
    26,875
    17,634
    0
    Location:
    Indiana, USA
    Vehicle:
    2010 Prius
    Model:
    IV
    Can you post a photo? You're not talking about something in the long white fusible link assembly?
     
    #21 ChapmanF, Aug 29, 2025 at 9:41 AM
  2. JC91006

    JC91006 Senior Member

    Joined:
    Nov 10, 2013
    16,723
    8,546
    0
    Location:
    Los Angeles, CA
    Vehicle:
    2008 Prius
    Model:
    II
    Oh now you're onto something. Maybe someone jumped started this car, accidentally reverse polarity the battery connection (if you did it in the rear, it could happen because of the tight space). That will blow the fusible link and the car won't start
     
    #22 JC91006, Aug 29, 2025 at 10:22 AM
  3. Hayslayer

    Hayslayer Member

    Joined:
    Nov 6, 2024
    284
    161
    0
    Location:
    USA
    Vehicle:
    2009 Prius
    Model:
    Touring
    If there was a reverse polarity jump performed that opened the fusible link in the white plastic housing (with clear plastic top) I saw a way to work around it on this site if the car needs to be moved. The post mentioned it should definitely only be temporary, as it basically used pennies wedged on each side of the blown link to get continuity back. A bit risky, but sometimes that's required if you need to get a car moved. If you don't know what caused it to blow, I don't think I would do that penny trick. I'll try to find that post, it's been months since I read it.

    Found it, it even has a photo.

    2008 Prius won’t start | PriusChat

    Don't forget, when a reverse polarity jump occurs, it normally blows a couple fuses in that fuse box also.

    Good luck!
     
    #23 Hayslayer, Aug 29, 2025 at 1:53 PM
    Last edited: Aug 29, 2025 at 2:02 PM
  4. Belliott

    Belliott Junior Member

    Joined:
    Jul 26, 2020
    22
    4
    0
    Location:
    Maryland
    Vehicle:
    2006 Prius
    Model:
    Two
    So in conclusion, The original post that the SKS icon was blinking regardless was incorrect. The car exhibited the following symptoms:

    -on first Power button press all that was achieved is the Power button lighting green and SKS icon ceasing to flash
    -On second power button press, button turns orange, SKS icon stays off and CEL illuminates.
    -car has no brake lights at any time.
    -power locks do not operate by the fob or rocker switch button on interior door panel/armrest
    -center display never turns on
    -brake pedal pulses and generally acts as normal, which might not seem normal if you are not in tune with its normal pulses and clicking noises.
    -Gasoline engine never turns on.

    The cause was found to be a fault in the fuse box that had been fixed by a previous owner, and that fix had gone bad.

    There is a fusible link (a thin squiggly bit of metal between two plates that can burn away if there is too much current.) in one of the distribution bus bars in the under-hood fuse box. It gets juice from the positive jump point under the red cover and distributes it to the items that should Always be hot, like brake lights, the power locks, etc... A previous owner apparently diagnosed this and fixed it by crimping a glob of metal to those two plates to bridge the gap. That piece of metal slid forward, breaking the link and electrically disconnecting those "always hot" items from their supply of power.

    I slid that glob of metal back in place and the car behaved normally. I then engineered a more permanent solution by cutting a groove in a binder clip so it would sit down below the step in the forward plate, sanding the paint off the inside surfaces, removing the "legs" of the clip, slathering it in no-alox so it wouldn't oxidize, and placing that so it contacted both plates. The plastic cover keeps the clip from moving upward. This seems like a duct tape solution, but given how tight it is in that box, all my other solutions involving soldering wires to the plate that had inline fuses or terminals on that bolt by the jump point simply would not fit in there. I know the real solution is replacing that plate. Seems like opening a can of worms to try to replace just that plate or the entire box.
     

    Attached Files:

    #24 Belliott, Sep 1, 2025 at 11:40 AM
  5. ChapmanF

    ChapmanF Senior Member

    Joined:
    Mar 30, 2008
    26,875
    17,634
    0
    Location:
    Indiana, USA
    Vehicle:
    2010 Prius
    Model:
    IV
    It isn't replacing the metal plate or the entire box, it's replacing that long white windowed assembly that has the plate in it. That's the fusible link block assembly. (That shows the MSRP; you can click dealer links to see their discounts. You can also buy from a recycler, but check any used one carefully to make sure none of its links are blown!)

    It unclips and lifts straight up out of the fuse box* and has some bolted connections and at least one plug-in connection on the bottom. The wires are long enough to lift it out and transfer the connections. Then you pop the new one right down in the slot.

    You can refer to this thread for more instructions on changing it:

    How to change Fusible link under hood | PriusChat

    Your improvised fix is to be presumed unsafe; chances are very slim it would blow at anything close to the intended current in the case of a fault somewhere. The results could be damage to much more expensive parts, destruction of a wire harness (expensive both as a part and in replacement labor), or fire with property damage or personal injury.


    * before I did my first one, I bought a fusebox from a recycler that had the part in it, and practiced pulling the part out of that. My practice run was difficult, because that fusebox had been sitting in a recycler's yard in the sun and the wire insulation got very stiff. Pulling the white assembly up out of the box was really hard because of the stiff wires. But then after I'd practiced, I went and worked on a real car with the fusebox protected under the hood, and even though the car was like a dozen years old, the part was easy to pull upward.
     
    #25 ChapmanF, Sep 1, 2025 at 12:07 PM
    dolj and Brian1954 like this.
(You must log in or sign up to post here.)
Page 2 of 2