Gen2 bricked CM, ECU, or Hybrid battery?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by PriusOwner428, Sep 27, 2025 at 12:15 AM.

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  1. PriusOwner428

    PriusOwner428 Junior Member

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    2008 Prius
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    2008 sat unattended in garage for 2 weeks.
    On return it would not start or go into ACC.
    Dash is dead. Could this be a hybrid battery gone dead?
    If it was left with 1 or 2 bars on the hybrid battery charge level, could the hybrid battery gone bad and be causing the following symptoms?

    When the power button is pressed with a working key fob inside the car nothing happens:
    No green LED on start button.
    No starting of the car.
    No going into ACC mode.
    No Ready indication.
    No display on the dash (Combination meter items like fuel gauge, odometer, gear, speedometer AND no Maint reqd, check engine, TMPS, ABS, key in car, airbag, or Triangle of death flash).

    Things that do work:
    Horn
    Headlights
    Brake lights
    Open door icon
    Internal cabin lights
    12V battery (verified good)
    +++ No key icon (when tried without key inside the car) ***
    Door lock/unlock by remote AND by buttons on door

    Other Info:
    As stated the 12V battery is good.
    Both remotes have new batteries and can lock/unluck doors, will trigger "no key" icon when try to start car without them inside the car.
    AM2 fuse is good.
    Fusible links in the engine compartment fuse box all look good.
     
    #1 PriusOwner428, Sep 27, 2025 at 12:15 AM
  2. dolj

    dolj Senior Member

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    You will need to clarify by what process you determined the 12 V battery is "good".

    Did you check that the CR2032 lithium batteries you installed in the remotes had a voltage of 3.3 V or better?

    Given all the symptoms you listed, you have a 12 V supply issue. If indeed the 12 V is "good", then you need to start checking connections and cables.
     
    #2 dolj, Sep 27, 2025 at 1:00 AM
  3. T1 Terry

    T1 Terry Active Member

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    Check the safety fuse for the hybrid traction pack, but my guess is the cell link connections have built up so much corrosion that there is a break in the series cell chain, or the battery has given up the ghost completely ....

    Can you hear the contactors close when you go to ready mode? It could be a failed contactor .....

    T1 Terry
     
    #3 T1 Terry, Sep 27, 2025 at 1:49 AM
  4. PriusOwner428

    PriusOwner428 Junior Member

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    12V was determined as good by several methods. Took it to Auto Zone for testing. Swapped it with a battery from a working 2008 Prius - the working Prius continued to work. The bricked Prius with the battery from the working Prius continued to show no signs of life.

    CR2032 in BOTH remotes are new and at 3.3V. Also both remotes remotely open and close doors. When a remote is inside the car it does NOT flash the "no key detected" warning. When there is not a remote inside the car, it does flash the "no key detected" warning. Plus physically putting the remote in the slot does not change anything.
     
    #4 PriusOwner428, Sep 27, 2025 at 2:26 AM
  5. PriusOwner428

    PriusOwner428 Junior Member

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    I guess I'm not sure what or where the "safety fuse for the hybrid traction pack" is. But if it's the fusible link in the engine compartment fuse box - it looks OK. See attached pic.

    It won't go to ready mode. When the power button is pushed there is no noise and no lights/LEDs on the dashboard.
     

    Attached Files:

    #5 PriusOwner428, Sep 27, 2025 at 2:38 AM
  6. T1 Terry

    T1 Terry Active Member

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    Pull the plastic tray out from under the false floor in the back. Up the left hand side of the battery is an orange handle, pull it up and slide it up and the safety switch and fuse will come out. Check across the fuse using continuity on a multimeter, when you refit the safety switch, be sure to push it down after locking it into place, that closes a second safety circuit.

    T1 Terry
     
    #6 T1 Terry, Sep 27, 2025 at 5:33 AM
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