Battery dead (?) and Prius stuck in ACC mode (maybe?)

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Hour of Gold, Nov 28, 2013.

  1. Hour of Gold

    Hour of Gold New Member

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    My 2004 Prius has been experiencing 12v battery drains (usually totally understandable ones, from dome light left on, door ajar, etc.) off and on since I got it (used, this time last year). Last week, I drove it to my son's preschool and after class was done two hours later, the car wouldn't start even though no doors were ajar or lights were on. I had left the headlights turned on (which, they normally power down after the car is shut off, but maybe that was too much for it?) I turned those off and within 20 minutes, I tried it again and she fired up and on with no problems (except the usual message about the parking being abnormal).

    Last night - same situation, only it can't be restarted in the same quick-fix, self-healing way. (It's much colder here now, if that's a thing.) This morning, I tried to go into ACC mode to run the 12v battery test, but there wasn't even enough power to light the nav screen. Tried jumping off the battery with a neighbor's gigantic truck - nothing. (This has worked in the past, but not this time.) Now, the car seems to be stuck on in ACC mode but with only the orange "check engine" light illuminated. Is it even possible for the Prius to be trapped in ACC limbo? I can't power it down to get the CE light off.

    I'm assuming the 12v is damaged/dead (not sure if it is an original or not - I know I should just go look, but I don't know exactly what I'm looking for to tell whether it's manufacturer or aftermarket battery, and it's so cold out that I don't even want to go back out there). Will it being "stuck" in ACC mode (presumably?) hurt the Big Cahuna hybrid battery or the rest of the car - is that even a possibility, or am I overthinking this? Do I need to disconnect things to get it powered down?

    Thanks in advance, and apologies if this issue has been addressed elsewhere - I searched and found lots of helpful threads, but if there's one with this same exact scenario I must have missed it.

    TIA!
     
  2. uart

    uart Senior Member

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    Try holding the power button on for about 5 seconds or more until it fully turns off.

    Yes hopefully it's just the 12V is so dead that it can't even be jumped, and not a failed jump start and a fried inverter.

    BTW. Wouldn't it have been easier to just change out the 12V battery months ago when you knew it was going bad? :rolleyes:
     
  3. Hour of Gold

    Hour of Gold New Member

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    Hmm, I hope you're right about that first!

    I didn't know it was going bad until I suspected as much last week ... when a battery dies after the door sits ajar all night, that seems more like a reasonable cause of perfectly understandable drain than a huge red light saying, "Oh, obviously this battery is kaput." Not that I really would have had the money to spend on the battery just on a hunch it might be dying. Just sayin'.

    Thanks for your response.
     
  4. bisco

    bisco cookie crumbler

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    these are not like regular car battery's. a couple of drains and you've stabbed them in the heart. time for a new battery no matter how old it is and get an optima yellow top, they are much more agreeable to being drained. all the best!(y)
     
  5. Hour of Gold

    Hour of Gold New Member

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    Right? I am learning as I go on the Prius battery issue - earlier today I ordered one of the Optima ones you suggested. I think while the car is down I may skim through the Priuschat site and see if I can do a quick study in any other should-know tips before I get back behind the wheel ... just a crash course so I don't get caught like this on the future with other Prius-specific issues.

    Thanks again. :)
     
  6. bisco

    bisco cookie crumbler

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    very smart.
     
  7. uart

    uart Senior Member

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    Yeah sorry Hour of Gold, I guess I was assuming that you knew what I know about the Prius 12V battery. When you said you’d been having issues with it draining for a year, and had jumped it a few times already, then it was pretty obvious to me that it was near death. Basically it’s what bisco said, once you have fully drained it a few times it’s dead. The difference between a Prius and a regular car is that the 12V battery doesn’t have to crank the engine, so it can get *really* weak without you noticing.

    Honestly we see lots of cases posted here where people just keep limping along on a really weak 12V battery without replacing it. You’d be amazed how often it ends in tears with a blown inverter and a four digit repair cost due to a bad jump start.
     
  8. Hour of Gold

    Hour of Gold New Member

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    So, what do you think the odds are of having a 12v battery that's totally deadsel, vs. having blown the inverter? Is there any way to tell besides changing the battery and not having it work? If there's a four-digit repair involved the car will likely be totaled out. Gah ... I've been having nightmares about searching for another Prius and going to a car lot owned by someone named Crazy Ed ... I hope it's not a self-fulfilling prophecy.

    Thanks for your advice!
     
  9. uart

    uart Senior Member

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    As long as you were really careful about the polarity of the jump start then it's most likely just a dead battery.

    If the jump leads got connected reversed, even for just a second, then it can mean a blown inverter. Even then it's not always the case, sometimes it just blows a fuse.
     
  10. bisco

    bisco cookie crumbler

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    there is a battery self test on the mfd, and a way you can test it with a volt meter. search the threads for info.
     
  11. Hour of Gold

    Hour of Gold New Member

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    Yikes ... I left ex and neighbor in charge of jumping ... the end of times may be near.
     
  12. uart

    uart Senior Member

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    Ouch, that doesn't sound good.

    It still might be ok though. Can you get hold of any known good battery (from anywhere) and just connect it via jump leads (with your existing battery disconnected). That's a quick way to test is everything is still ok on the Prius.
     
  13. Hour of Gold

    Hour of Gold New Member

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    I got the new battery in today's mail, read the instructions, watched a video about how to change the battery, and decided to do what I could to get ready before daylight fades. I removed the battery cover and the black plastic harness, and saw that there is standing water in the well where the battery fits. I can't tell how much since I don't know what it looks like normally in there ... the water is touching the old battery. What should I do? Proceed? Take any special precautions? I don't know enough about this kind of thing to make a confident guess.
     
  14. dorunron

    dorunron Senior Member

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    It is a common problem or so it seems. See this link for more information.

    Water leak...into spare tire area etc | PriusChat

    As far as your car is concerned, I would attempt to find the leak and repair same. You are not the first person to report this problem.
     
  15. Hour of Gold

    Hour of Gold New Member

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    Thanks, I was just looking this over in the threads! I am trying to find more about a possible plug that I could unstop to release the water, that I read others asking about. Is that right, or do I need to bail out the compartment manually for the time being?

    Thanks again!
     
  16. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Reach around, and if you can find a plug to remove, then take it out. Otherwise use a cup and paper towels to bail out and dry the area.
     
  17. Zedhomme

    Zedhomme Member

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    If the water is where the battery sits, you might be able to pull out the grommet holding the vent tube in the floor and let it run out. It's in the way anyway for swapping the battery.
     
  18. Hour of Gold

    Hour of Gold New Member

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    Sorry to keep hitting everyone up ... is there a good video out there to take me through the steps of changing out the battery? I've been searching, but I have a cold and a babbling toddler and can't really concentrate with the congestion and 100 dB conversation. :)

    Thanks in advance!
     
  19. usnavystgc

    usnavystgc Die Hard DIYer and Ebike enthusiast.

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    There are several on YouTube. Just do a search for "Replacing Prius 12V Battery" and watch a couple and find the one that "speaks to you".
     
  20. Hour of Gold

    Hour of Gold New Member

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    I can't find one with the complete process (that I could tell), and I'm not really able to search effectively right now ...
     
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