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can you diagnose the problem here? intermittent start

Discussion in 'Gen 2 Prius Main Forum' started by ericspoor, Jan 3, 2019.

  1. ericspoor

    ericspoor Member

    Joined:
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    Location:
    austin
    Vehicle:
    2005 Prius
    Model:
    Base
    heres the sequence of events, give me your thoughts:

    1. a couple months ago: it got cold here in texas. this is the first cold since owning my prius. it got drastically cold overnight. i drove to work. i work till 5. i clock out and hit start- combo meter is dim, RTOD, other lights, no ready status. i turn car off. i hit start again- prius is able to reach "ready" status and i drive home.

    2. one month later- same occurence as above


    3. present day: temp drops overnight. attempt to start car in the morning- car wont move to ready status, single gas bar in gas gauge is blinking, other lights incl check engine. run the codes- c2300 and c2318. I determine that given the prior events and the codes present and the blinking gas bar that this is textbook 12v battery going bad.

    4. I install new 12v, oem toyota. car starts and moves into ready. i turn car off after 10 seconds. i attempt to start again 3 mins later and the car is totally dead- no lights nothing on the dash. jump the car front the front fusebox spot, car moves into ready and i and drive to work

    5. car sits for 4 hours while at work. after work im able to start car and drive home

    6. car sits overnight. the next morning (this morning)- i hit start to go to work. the dash lights up for a split second then the dash goes out and the car is dead.

    7. i uber to work. when i get home, i take a multimeter and measure the voltage from the 12v- it reads 12.62v in one instance and 12.45v in another. So the battery is good and holding a charge. over the course of getting the multimeter nodes to make contact im naturally interacting with the cables attached to the battery terminals, they get a little josling around. i also notice that the cables attached to the terminals are tight. i walk away from the car without attempting to start it


    8. later that night (tonight) i come back to the car and im able to start it normally. i check the battery again and notice that the nut holding the ground wire from the negative terminal to the unibody is loose considerably (easily moves using your fingers, not tight at all), i tighten the ground nut.



    what do you think is going on here? my theory is that the original problem was the 12v battery going out, then there was a secondary problem with the loose ground nut not being tightened after install which was periodically making ground and periodically not, causing intermittent delivery of power from the 12v, but (forgive my total electronic ignorance) does 12v power delivery cease when a ground is loose?


    id like to give a shoutout to matt at texas hybrid batteries. i gave him a call, when he picked up he knew my name despite interacting with him over half a year ago, and generously lent me his time to help with my issue. if youre in the dfw area or in roadtrip distance hes the perfect prius gen2 subject matter expert/master tech- give him your money with confidence
     
    #1 ericspoor, Jan 3, 2019
  2. JC91006

    JC91006 Senior Member

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    II
    Your problem is the loose ground, probably had nothing to do with the battery you replaced
     
    #2 JC91006, Jan 3, 2019
    Skibob, Raytheeagle and jerrymildred like this.
  3. TMR-JWAP

    TMR-JWAP Senior Member

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    Thank you for sharing this. You've done an excellent job of describing your problem and you've proven the validity of the advice provided multiple times by and to other members who have had similar symptoms. I would hate to try to count the number of posts here with similar symptoms. Almost always, the advice is to verify the battery condition, the battery terminal connections, the ground wire connection and the supply cable connection at the underhood jump terminal.
     
    #3 TMR-JWAP, Jan 3, 2019
    Skibob, Raytheeagle and jerrymildred like this.
  4. jerrymildred

    jerrymildred Senior Member

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    +1 to @TMR-JWAP and @JC91006.

    And, to answer your question, yes, the ground is just as important as the positive. Kirchoff's first law says that the current going out of a node on a circuit must equal the current going into it. The battery is one of the many nodes in a car's circuitry. If you disconnect the battery from the circuit, you no longer have a circuit because the current can't get back to the battery. A circuit, by definition, comes back to its origin.
     
    #4 jerrymildred, Jan 4, 2019
  5. ericspoor

    ericspoor Member

    Joined:
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    Location:
    austin
    Vehicle:
    2005 Prius
    Model:
    Base
    Thanks for the input all!

    You may be right about the original 12v not being bad in the first place. i wish i had tested the voltage before replacing it (whats the phrase? "Keep it simple stupid").

    That said, when i did remove it, it had a lot of corrosion on the positive terminal so it probably wasn't too terrible of a mistake to replace it
     
    #5 ericspoor, Jan 4, 2019
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