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Intermittent no power, lights, buzzers.. 2007, 200K miles

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by David Carlos Salaverry, Sep 3, 2024.

  1. David Carlos Salaverry

    David Carlos Salaverry Junior Member

    Joined:
    May 22, 2019
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    Location:
    Tucson AZ
    Vehicle:
    2008 Prius
    Model:
    Two
    • Vehicle and Initial Condition: Drove recent purchase 2007 Prius for 40 miles yesterday; upon exiting, the key fob failed to work, and the car had zero power—no lights, buzzers, or any electrical activity..
    • Intermittent Operation: Two hours later, the car started normally. Throughout the day, the car started without issues after being parked on three separate occasions.
    • Re-occurrence of Issue: Did 200 mile freeway trip, drove home and after parking, the car was dead again—no lights, buzzers, or power. No other symptoms, no warning lights, etc. Can't check codes with no start. Note: A week earlier, the car went dead overnight but I was able to jump start, drive errands with no problems
    • Current Condition: Today, the car remained dead. Voltage at the front jump start terminals measured only 2 volts.
    • Attempted Fix: Connected a fully charged new 12V extra battery, but the car still exhibited no power, lights, or buzzers.
    • Additional Steps Taken:
      • Battery Testing: Have not yet tested the rear 12V battery, hatch will not open easily.
      • Key Fobs: Replaced the batteries in both key fobs, but it made no difference

     
    #1 David Carlos Salaverry, Sep 3, 2024
  2. David Carlos Salaverry

    David Carlos Salaverry Junior Member

    Joined:
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    Location:
    Tucson AZ
    Vehicle:
    2008 Prius
    Model:
    Two
    Update.. I tried another jump start, no go, totally dead car. Next, I crawled in back, opened the hatch manually and as soon as I touched my multimeter to the 12v battery terminals to test voltage, the car beeped. Back in front, the dash was lit normally. However, I'm guessing it never shut down the night before as I did NOT push the power on button or press the brake pedal today.

    So.. my hunch is I have a bad shutdown problem that causes the dead no lights, no buzzers, no door locks problem. Anyone have ideas how to solve? I travel a lot and can't be crawling into the back to "kick" the 12v, especially loaded with car camping gear.
     
    #2 David Carlos Salaverry, Sep 3, 2024
    Last edited: Sep 3, 2024
  3. MAX2

    MAX2 Member

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    Location:
    Third Rock from the Sun
    Vehicle:
    2007 Prius
    Model:
    N/A
    You need a new 12V battery.
    Problems with battery discharge lead to electronics reset, you won't even be able to get into the car without a mechanical key, much less start it up.

    On Gen2 there is also a problem in the instrument panel. The capacitor on the electronic board loses its normal parameters and the panel does not turn on, you can not see either the speed or other indicators. It is necessary to replace the panel or, if possible, work with a soldering iron, replacing the capacitor.
     
    #3 MAX2, Sep 3, 2024
  4. mr_guy_mann

    mr_guy_mann Senior Member

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    Vehicle:
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    Four
    If the 12V was really discharged to the point of not powering anything (completely "dead"), then poking around won't suddenly make it come alive. Having a reaction when you disturb the 12V battery (even a little) suggests that there is a loose connection somewhere in the area.

    Could be at the battery posts, could be the negative cable at the body, could be the positive "quick connect" (big white plug).

    I would watch the dome light (while just the light is on but the car is not ready) while wiggling everything at / around the 12V battery. See if anything makes the light flicker or go out.

    Posted via the PriusChat mobile app.
     
    #4 mr_guy_mann, Sep 4, 2024
    Brian1954 likes this.
  5. Tombukt2

    Tombukt2 Senior Member

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    Vehicle:
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    When I'm in the back of the car and funny business is going on I'm usually looking for that hatch or door open light to be on steadily if that's flashing or going in and out the same problem possibly that you're chasing now the loose connections and all that have you had a problem in this new purchase where you don't see your gas transmission or speed display? That's a clue that will need to be addressed as shutting off the car will become more and more difficult especially if you don't know how this works and this is a new thing and you will run down your 12 volt and calls all kinds of havoc If you don't understand how this is working That's the CM monitor error You can read the codes when you do get the power on that's a good time to have your scanner plugged up so if this is going in and out you may have a chance to see what your scanner might be telling you.
     
    #5 Tombukt2, Sep 4, 2024
  6. David Carlos Salaverry

    David Carlos Salaverry Junior Member

    Joined:
    May 22, 2019
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    Location:
    Tucson AZ
    Vehicle:
    2008 Prius
    Model:
    Two
    MAX2.. the battery is relatively new. testing at the rear yesterday after the car came to life, I had 12.3 v

    mr_guy_mann.. I checked the battery posts and neg connect to frame, everything tight and clean, no signs of water infiltration. but a loose connection somewhere seems possible

    Tombukt2.. previous owner did a DIY capacitor replacement in the CM monitor. All dash lights working correctly. I've done this myself on my 2008 Prius which is currently in-op. The job is a bear!

    Update 1.. This morning, the car was active electrically. I attempted to fully charge the 12v with charger leads on the front jump start terminals. My automatic smart charger said "Battery Full 14v" and shut down. I moved the charger to the rear to connect directly to the 12v and the charger began to operate.

    Update 2.. I will jump back in when the 12v is fully charged later today.

    Note: This morning, voltage at the rear battery posts before charging was 12.6. Voltage at the front jump start posts was 12.3. Is this normal? Also. more weirdness that may be relevant.. the alarm system went off with honking horn when I tried to start the car this morning during the above testing.

    All.. this is a brain teaser. I greatly appreciate your expertise and willingness to help a fellow Prius traveler!
     
    #6 David Carlos Salaverry, Sep 4, 2024
  7. MAX2

    MAX2 Member

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    Location:
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    Vehicle:
    2007 Prius
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    N/A
    The charger should be connected directly to the 12V battery terminals, but the negative wire should be disconnected from the car body.
    12.3 -12.6 is quite normal for an auxiliary battery.
    When the car is turned on, the voltage may drop partially.
    Sometimes I had it drop to 10-9 V, but the impulse is still enough to connect the hybrid part and turn on "Ready" on the instrument panel.
     
    #7 MAX2, Sep 5, 2024
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