1. Attachments are working again! Check out this thread for more details and to report any other bugs.

2006 Prius 12V battery problem

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Rhonda124, Jun 5, 2018.

  1. Rhonda124

    Rhonda124 Junior Member

    Joined:
    Jun 5, 2018
    3
    0
    0
    Location:
    New Mexico
    Vehicle:
    2006 Prius
    Model:
    II
    A few months ago, my car started to die all of the time, but not fully if that makes sense? The engine wouldn't come on during initial startup, but I could still drive as the engine would come on only when I was on the gas pedal, I reset the 12V battery and everything was fine for a few days. Then, my dash would not come on when the car was started along with the engine, but again, it was still driveable and all my lights (headlights, blinker, etc.) were still working. This happens often, maybe every 4 to 7 days, easily being fixed with a reset.

    However, I recently drove a long stretch of about 500 miles, and about halfway through, I noticed the terrible gas mileage and the draining hybrid battery, and behold my engine wasn't running like it should. I pulled over and when I turned the car back on the dash wasn't working which confirmed what I thought, it died while I was driving!

    I do have a brand new 12V battery installed because I thought that may be the problem but that didn't fix it. Any ideas of what it might be? TIA
     
  2. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    107,686
    48,936
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    probably the hybrid battery, is it hot there? how many miles on her?
     
  3. Rhonda124

    Rhonda124 Junior Member

    Joined:
    Jun 5, 2018
    3
    0
    0
    Location:
    New Mexico
    Vehicle:
    2006 Prius
    Model:
    II
    Yes, I’m in southern New Mexico so it’s over 100 F every day. She’s got about 156,000 miles. But the hybrid battery seems to work like normal, except when this happens, and returns to normal when I unplug and replug the 12V battery.
     
  4. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    107,686
    48,936
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    if the battery gets too warm, the computers will shut it down and your engine only. might be worth checking the cooling fan and intake grille. no dash lights?
     
  5. ericbecky

    ericbecky Hybrid Battery Hero

    Joined:
    Mar 12, 2004
    4,365
    3,209
    1
    Location:
    Madison, Wisconsin
    Vehicle:
    2005 Prius
    Model:
    Two
    Unplugging clears the memory and makes it temporarily"forget" that it is broken.

    It does not fix anything.

    The car will soon remember that it is broken.

    Doing a reset this way is a brute Force way to clear a code and can cause other components to get damaged since you are forcing it to operate in a broken state even for a shirt time.

    Favorite story of this is a customer with a failing hybrid battery. He did not want to tow it to me or have me come to his location. He drove it 30+ miles stopping many times along the way unplugging and replugging the 12v.

    He made it within a mile of the shop, but got stranded in traffic because of the loud POP sound, smoke, and acrid smell coming from his high voltage battery!!!

    Don't be that guy.

    Could be other problems. Here are some wild guesses...
    - failed inverter pump, whih then leads to the inverter overheat/damage.
    - failed inverter
    - failed transaxle
    - short in high voltage system
    - failed hybrid battery
    - failed or blocked HV Battery fan.

    Get the codes read by a parts store or mechanic.
    Or spend $75 to get these 3 things to read codes yourself
    - Android phone/tablet (~$50)
    - Elm 327 Bluetooth OBDII adaptor (~ $20 or less)
    - Torque Pro app (~$7)

    We can only guess at this point but with more data we may be better equipped to point you in the right direction.
     
  6. wjtracy

    wjtracy Senior Member

    Joined:
    Sep 19, 2006
    11,311
    3,588
    1
    Location:
    Northern VA (NoVA)
    Vehicle:
    Other Hybrid
    Model:
    N/A
    I just put in a new 12v Optima yellow top.
    What brand did you go with on the 12v?
    I assume the new 12v was in for the 500 miles trip?
     
  7. Andrew_Ph

    Andrew_Ph Junior Member

    Joined:
    Nov 26, 2017
    46
    4
    0
    Location:
    MI,USA
    Vehicle:
    2007 Prius
    Model:
    II
    I am thinking the dash isnt caused by your battery but the usually suspect solder joint in the dash electronic assembly, sometimes caused by weather changing. It can be corrected by removing the aux battery for a moment.
    The engine never comes on exactly at startup, only 7 seconds later.
    If the HV batteries are getting too low, you should see a car with an exclamation point come on in the LCD screen.
    I would recommend getting the codes checked, either with torque or at autozone, but they might not see prius specific codes.
     
  8. Andrew_Ph

    Andrew_Ph Junior Member

    Joined:
    Nov 26, 2017
    46
    4
    0
    Location:
    MI,USA
    Vehicle:
    2007 Prius
    Model:
    II
    the statement engine not running like it should is a bit vague, but if the inverter/charger is not working right then could be charging and spark problems. real easy to check the voltage while the car is running, should be over 14v, i think. can even be done from the dash with the maintenance mode sequence.