2008 Prius will intermittently not start (battery is good)

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by kleo, Dec 21, 2016.

  1. kleo

    kleo New Member

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    Hello! I've been having problems with my Prius and have taken it to a dealer and a mechanic and they have not been able to help me yet. I'm trying to find someone more reliable / with more experience to help me, but in the meantime, does anyone have any suggestions?

    Here is a summary of what is happening:
    - Car sometimes starts and sometimes does not start
    - The doors are able to lock/unlock, the hatchback can be opened, all interior lights turn on, so all other 12V battery functions are working
    - The key fob batteries were recently replaced, both of my 2 keys have the same behavior, and no issues locking the car, so it doesn't seem to be a key issue.
    - When the car does not start it makes a noise when you push the start button, but that is it. Nothing on the dashboard turns on.
    - Some ways to get the car to start: try again later, disconnect and reconnect the battery, lock and unlock the doors a few times randomly

    Here is the timeline of everything that has happened for more clues:

    About 3 weeks ago: On a rainy day when I was driving, the red exclamation triangle warning light came on. "There is a problem with the transmission "p" lock mechanism. Park your car on a flat surface and fully apply the parking break." It went away the next time I started my car. A few days later on another rainy day it came back on. It went away again.

    About 2.5 weeks ago: The car would not start. It would not jump. Later someone else tried to jump it and it worked. The P-lock error message came back up again. I took it to the dealer. They said there was nothing wrong with my car or battery. The next day it wouldn't start again. The dealer said they would not help me because I had an Optima battery. Batteries + Bulbs would not replace my under warranty battery because the battery was testing perfectly fine.

    2 weeks ago: I ended up buying a new battery because no one would help me until we could rule out battery problems. The car worked for 2 days then I was out of town for a week.

    1 week ago: The car would not start or jump again. It was towed to a mechanic who has confirmed again that it is not a battery issue because the battery is testing fine. He says all the fuses look fine. He figured out a few things that would make the car work again, like disconnecting and reconnecting the battery and locking and unlocking the car a few times. He thinks it's an electrical issue, but he's had my car for a week now and hasn't figured it out yet.

    Help?
     
  2. valde3

    valde3 Senior Member

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    No fault codes? If there are some what do freeze frame look data in them look like? Maybe there’s bad connection somewhere in 12V system? Does it do the same thing with ley in slot and without? Or do you have the model without the SKS?
     
  3. usnavystgc

    usnavystgc Die Hard DIYer and Ebike enthusiast.

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    Everything you describe are classic symptoms of a weak 12V battery. I don't care what any mechanic or dealer has told you, your 12V battery is weak/dying or there is a bad connection. I am very confident it is the former. Mechanics/dealers are notorious for misdiagnosing or identifying a weak 12v battery in a Prius.

    If you got a "brand new" battery and this is still happening, the battery is bad or the connections are bad. You might try unplugging and reseating the connectors on the positive cable of the 12v battery (these are white plugs just down the cable).
     
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  4. bisco

    bisco cookie crumbler

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    welcome!
    agree^^^ is it the original battery? if so, just replace it, it's gonna die soon anyway.
    if not, you really should do a definitive voltage/cranking amps test if you don't want to just replace it. you can also check the battery cable connections, especially the negative to body.
    another thing would be to back up against a wall or have someone watch your brake lights, to see how hard you have to step on them. the interlock switch may need adjusting.
    all the best!(y)
     
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  5. kleo

    kleo New Member

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    Thanks for the responses!

    There are no fault codes. When it turns on everything works fine and tests fine and there's no record of anything going wrong.

    It does the same thing with the key fob in the slot or not.

    The 12V battery that was in it when I first started having this problem was only 1.5 years old. I bought a brand new battery about 2 weeks ago anyway, and it still is having the exact same problems.

    I will check into the interlock switch.
     
  6. bisco

    bisco cookie crumbler

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    still worth testing the battery voltage, just to make sure your not on a wild goose chase. some new ones come needing a charge.
     
  7. usnavystgc

    usnavystgc Die Hard DIYer and Ebike enthusiast.

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    Bisco is correct. Assuming the interlock your referring to is the brake light switch, the brake light switch can really be ruled out because the error you're getting says to put the car in park. That is because the "Park" signal to the ECU is so weak, the system can't read it as being there (which is a classic indication of a weak 12v battery or a loose connection).
     
  8. goldfinger

    goldfinger Active Member

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  9. wmatten

    wmatten Junior Member

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    I had very similar symptoms in my 2008 -- it would intermittently have no power to anything, only after it was parked for a bit. I had replaced the auxiliary 12V about 14 months ago, and it still showed 12.3 V at the terminal under the hood. Last week I checked it's connections and the positive terminal connection was a tad loose. Tightened that up and all is good, so far. I guess it took 13.5 months to loosen up.
     
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  10. edthefox5

    edthefox5 Senior Member

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    The definitive test is to get a voltmeter. Buy one. Open the hood take the black plastic cover off the fuse box on the right. Flip open the little red
    Cover revealing the 12 volt jump lug. In D.C. Volts measure from their to ground. Write it down.
    Then with voltmeter still connected while someone pushes the Start button monitor the voltage swing.how low does it go?

    You put a new battery in then u split for a week and whatever killed the first battery killed the second battery.

    Also a good trick is at night before u start the car turn on the headlights. Then with them on start the car. If they dim or dip down your 12 volt
    Is ready to leave u.

    You may have light on in the back of the car and it's killing the battery
    Or the back hatch is ajar or u have kids getting in the car and leaving
    Door ajar.

    People with consistent 12 volt issues always have one thing in common.

    They don't arm the alarm every time they get out of the car no matter where they park especially final park in garage. That will alert u to light on or door ajar.
     
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