Prius sat for 4 months, battery is dead - how to restart?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by dipstick22, Mar 2, 2025.

  1. dipstick22

    dipstick22 Junior Member

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    The backstory is a divorce and a neglected 2008 Prius with just under 300,000 miles. The 12-volt battery is now completely dead. The car was starting to have intermittent problems while driving (VSC coming on under normal conditions). My first question is whether it is worth even buying a new $250 battery only to find out that the car is beyond repair. I have a friend with a Gen2 and was thinking of asking if I could "borrow" his battery to see what happens when I put it in and try to start up. Do I need to do anything special when I put the battery (new or borrowed) in the car?

    Second question - how can I find someone (other than the Toyota dealer) who works on Prius' in central Delaware?
     
  2. MAX2

    MAX2 Senior Member

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    Without a 12V battery you will not be able to start the Prius properly, so this is the first thing you need to do.


    If errors appear, then you need to diagnose the systems.
     
  3. dipstick22

    dipstick22 Junior Member

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    Thanks. I was concerned that I would be required to go through some kind of extensive "setup procedure". Hopefully the factory default settings for things will take over.
     
  4. MAX2

    MAX2 Senior Member

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    Have you used this hybrid before?

    When the car is standing still for a long time, problems can appear in different places. If something goes wrong, you can contact the forum for help.
     
  5. JC91006

    JC91006 Senior Member

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    You can simply jump start the car and see if there are other problems, it should be able to run but might give you a battery error. Chances are your big HV battery will probably have issues as well (depending on the age of that battery)
     
  6. dipstick22

    dipstick22 Junior Member

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    MAX2 & JC91006 - We are the original owners of the car since 2008. I know it "like the back of my hand". At about 295,000 miles, we loaned it our son-in-law and it was running fine. Then came the affair and separation and divorce. We took the car back but he said it had been "acting strange". I drove for a few weeks and saw 2 occurrences of the VSC kicking in for no reason under normal driving conditions. But it never threw a code. The hybrid battery was replaced at 190,000 miles and is not coding. For a variety of reasons, the Prius sat idle for about 6 weeks and when I tried to start it, the 12V battery was dead beyond recharge. From other responses, it sounds like installing a working battery would not require any special actions. So I'm heading down that path. I have a friend who also has a Gen 2 Prius. I think I'm going to ask him to let me "borrow" his battery to see if my Prius starts up and runs. If it does, I'll buy a new battery and give it to him.
     
  7. JC91006

    JC91006 Senior Member

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    Just go to costco and buy a battery for $200. The installation is simple and it should fix your car. If you have the time to remove and install a friend's battery, you should just install a new one for $200 and call it a day. VSC will flash if you run over uneven pavement, it is a normal characteristic of this car.
     
  8. BiomedO1

    BiomedO1 Senior Member

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    IMHO; just jump start it - rather than play musical battery swap or replace it. The car will run strange for a few hours or days, while the sensors recalibrate themselves, due to the battery issue and lost ECU settings. You may even get a few phantom errors. Erase them and see if they come back after you've make sure the battery issue has been solved.

    Hope this helps....
     
  9. Dion Kraft

    Dion Kraft Member

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    I had my 2004 Prius sit for 3 years and the 12 volt battery even with trickle charge eventually became very weak. But anyways I bought a AGM battery from Autozone - they have two versions..one for non-smartkey and one with smartkey. But upon getting it started I encountered some faults like error display but repeat starts cleared that up as well as a little test drive helped. I lost the use of my Smartkey totally so I had to reprogram them but that was easy for Smartkey cars not like the non-smartkey where you have to go through the "Chicken dance" routine. But if you borrow your friends battery..it will not hurt his car so that may be the bargain option if your not sure as to what condition your car turned into. Its a gamble but its your call - Good Luck !
     
  10. dipstick22

    dipstick22 Junior Member

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    Hey everybody! I'm back on this topic after some eventful weeks (not related to the Prius). The latest updates are:
    1. I replaced the battery and the Prius started up OK (with some coughing and sputtering)
    2. I drove it for about 20 miles over a few trips and noticed that it was "running rough".
    3. At one point, the Check Engine light came on with P0420. I cleared that code and it has not recurred, but it is still running rough.
    4. I have NOT had any recurrence of the VSC
    I now have it at 299,975. I drive it about every other day. It's getting about 45 mpg. I plan to do a tune-up on it since I think it's probably 100,000 miles overdue. I plan to use the kit available from Amazon ASIN B07NKBYNBZ. I watched some videos that suggest it is not overly complex other than reaching the plugs.

    I'm open to suggestions or questions on any of the points above.

    As always, thanks to you folks for sharing your experience and expertise.
    Randy
     
  11. pasadena_commut

    pasadena_commut Senior Member

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    Is the car still running on the tank of 4 month old gasoline? It might run better with a new tank of gas. Perhaps throw a bottle of Techron in too, to try to clean up whatever may have stuck on the injectors and elsewhere in the fuel system while no gasoline was moving through the system.

    Unused cars are like magnets for rodents. Some of the suggestions below reflect that.

    Check all the fluid levels. Check the air filters for the motor and the cabin - there may have been rodents in there making holes are storing nuts.

    Maybe clean the throttle body and MAF as well. If you're going to do one you might as well do the other at the same time.

    I wouldn't think the spark plugs would care much about sitting for four months, at least once they had been running for a few seconds. The coils also won't care if they sat unused. If there were rodents under the hood some wires might be chewed though.

    That error code relates to the catalytic converter. Maybe a family of roasted rodents and their nest partially clogging it downstream from the matrix in the cat?
     
  12. Mendel Leisk

    Mendel Leisk Senior Member

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    That's basically just someone compiling a shopping trip for you. From the product description:

    This the genuine Toyota Prius 2004-2009 tune up service kit. We have put together the oil filter, drain bolt gasket, engine air filter, cabin air filter, 4 spark plugs, and wiper blade refills. NOTE the refills only work with the original Toyota wiper blades. Please contact us to verify fitment if you are not sure.
     
  13. bisco

    bisco cookie crumbler

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    don't buy anything critical from amazon, it's all chinese counterfeit junk. get spark plugs etc from an online toyota dealer
     
  14. Mendel Leisk

    Mendel Leisk Senior Member

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    Or a bricks-and-mortar dealership, they'll have all this stuff. If you've got another transportation option.
     
  15. dipstick22

    dipstick22 Junior Member

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    Thanks for the quick replies! I've never used any kind of additives to fuel or oil. I change the oil every 5,000 miles with Mobil 1. But I wonder if a fuel additive might help. Thoughts?
     
  16. AVTrainz

    AVTrainz Junior Member

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    Back before we sold our Gen 2, it sat for a few years, and I agree that the main battery will probably be a trouble point. By the time we tried to jump ours, not only was the aux battery depleted but so was the main. Long story short, we tried jumping for a long time and couldn't even get an interior light to flicker on.
     
  17. MAX2

    MAX2 Senior Member

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    The interior light is the responsibility of the 12V battery.
     
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  18. AVTrainz

    AVTrainz Junior Member

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    Exactly. I'm pretty sure that the 12v had been done for quite awhile by that point. We didn't ever replace it after that situation because we sold the car not long afterwards.