Issue with Prius not Starting anymore. 12V battery replaced recently.

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by DKM, Mar 21, 2021.

  1. DKM

    DKM Junior Member

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    Hi Everyone,

    My Prius has failed to start several times over the last few weeks, I'm hoping to get some advice on the cause.

    Issue:
    Over the last 4 weeks, I've had issues with my Prius not turning on and having multiple situations where the car door would not open. I then have to call roadside assistance to get a battery boost. If you're interested to know more details about what these situations were feel free to refer to the bottom of my post for more info.

    Actions Taken:
    I have attempted to look into what the problem may be on my own but could use guidance from more knowledgeable people such as yourselves. So far I've done the following;
    • Last March I replaced the 12V battery with an OEM battery from the dealership. Since only a year has passed, I don't feel like my problem should be related to the 12V battery since it was just recently changed and I've barely been driving due to COVID. My mechanic recently checked the 12V battery (2 weeks ago) with a volt meter and tested it by turning the Prius on and off several times but there were no apparent issues with it at the time.
    • I checked the engine oil underneath the car hood and it was full.
    • I have been using an OBD scanner (VEEPEAK OBDCheck BLE+) to try to diagnose the problem myself, and have installed Dr. Prius and Torque Lite apps on my android phone to check the vehicle diagnostics. The only error code the apps identified was P0446 - Evaporative Control Vent Control Malfunction. I'm not sure if this error code has anything to do with my issue mentioned above. Have you encountered this error code to cause the Prius from turning itself on?
    • As I've been using the Dr. Prius and Torque Lite apps, I've found a wealth of diagnostic information such as the pack voltage, discharging rate, and state of charge. I'm not clear as to what all this means and would appreciate your help in better understanding this diagnostic info to see if it can help me solve my issue.
    Thank you very much for your help! Any ideas would be most welcome.

    ===================
    Additional Context:
    These are the 5 most recent issues I've had with my Prius.

    1) Parked car for 15 minutes to go shopping only to come back to find the car unresponsive. The electronic locks, windshield wiper were not working. The car required a battery boost.

    2) Car parked at home. Tried starting the car in the morning but faced the same issue where I couldn't even open the car door. The key fob wouldn't open it. Once I got inside with the manual key, the car did turn on. However, I noticed that the fuel gauge flashed several times. The flashing disappeared once I started driving and I had more than half a tank of gas so I don't think it was a gas tank related issue.

    3) While driving, a red triangle symbol on my dashboard popped up. Afterwards, I drove to my mechanic and I had the 12V battery checked. He said the battery was working fine. I tested the 12V battery myself using diagnostic mode with the following voltages;
    • Ignition Off (IG-OFF): 12.2V
    • Ignition On (IG-ON): 11.9V
    • Car Started: 14.1V
    4) Parked car for an hour. I tried to start the car but failed. Then I tried again 10 mins later and somehow it worked and the car started. Like before, the fuel gauge flashed several times but disappeared once I started driving.

    5) Same issue as #2. Car parked at home. Tried starting it in the morning but couldn't get inside the car. Smart sensor unlock didn't work, I had to use the physical key from the fob. This time, the car did not start like before, and I needed a battery boost.
     
    #1 DKM, Mar 21, 2021
  2. bisco

    bisco cookie crumbler

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    don't make this harder than it needs to be.

    if you spent any time here since covid began, you would know that you have a 12v problem due to your lack of driving like all of us.
    you may have killed your 12v, or it might just need a good charge.
    get yourself a ctek charger maintainer, or other quality brand.
    if it will hold 12.7+ volts over a week or so without the maintainer, you're okay.
    otherwise, you need a replacement battery under warranty.
     
    #2 bisco, Mar 22, 2021
    jerrymildred likes this.
  3. sam spade 2

    sam spade 2 Senior Member

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    What you "feel" isn't really important.

    NOT driving much is hard on 12 V batteries.
    Yours likely is failing.

    Once it gets low, the car won't completely recharge it by itself.
    Keeping the OBD scanner connected will drain the battery while the car is OFF, just making matters worse.
    Batteries can fail after only one DAY, much less one year.

    You need to get the battery tested, maybe in more than one place, because few "mechanics" really know how to do it.
    Your 12.2 and 11.9 numbers are NOT good.
    Since you got the battery from a dealer, it might still be under warranty.

    IF....you don't either give your battery a good overnight charge with a good charger OR get a new one and be sure it stays charged up......you will continue to have problems which have no obvious fix.
    Now you are just wasting your time. Really.
     
    #3 sam spade 2, Mar 22, 2021
  4. DKM

    DKM Junior Member

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    Thanks for the advice everyone. It has been quite stressful dealing with these car start issues, especially on top COVID. Initially, what I did was take the car to the dealer. What they found was the positive terminal of the 12V was extremely loose and wobbly. They tightened the connection so hopefully that explains some of the issue.

    When you say "tested" are there different kinds of tests or do you just mean a regular load test? I can have the dealer do this for $70. I have warranty so if the battery is faulty I can get it replaced. If the battery can be saved then getting a good battery charger/maintainer is the next step.
     
    #4 DKM, Mar 24, 2021
  5. sam spade 2

    sam spade 2 Senior Member

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    Given what was found already, I suggest that you get a battery tender NOW so you can be sure that the battery gets fully charged at least once.
    THEN.....if you continue to have electrical trouble, I would question why the dealer thinks they should charge you to test a part that THEY put in and is still under warranty.

    A voltmeter is a nice thing to have but not totally necessary.

    Some auto parts stores will test batteries for free. Just don't tell them too much about your situation; they don't need to know.
    Doing the load test twice or three times within a few minutes will sometimes "find" a weak battery that initially shows up "good".
    But testing one that is not fully charged can sometimes give a false failure too.
     
    #5 sam spade 2, Mar 24, 2021
    DKM likes this.
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