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Power at 12v no power at front terminals

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by BobThePrius, Aug 21, 2019.

  1. BobThePrius

    BobThePrius Junior Member

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    [Accidently posted this same post in the newbie forum, though I would try posting in the correct forum!]
    Hello PriusChat! Here is my situation:

    The car has zero power to any electrical function, however, it can be jump-started from the from front terminals under the hood, and all the car will run as normal and display no diagnostic codes (at least according to my bluetooth OBD2 reader.) As soon as the car is turned off however it shows no power to any electrical function. I have searched through this forum but have not found anyone with the same problem that I have (although I could have missed something.)

    Here is what I know so far:

    -The 12v battery is good and only a few months old (displays 12.94 v across the terminals and the guy at Autozone also confirmed the battery is good.
    -Across the terminals, under the hood, only 0.5v show up on my multimeter.
    -I cleaned and tightened all battery connections and terminals, and voltage is reaching the end of the negative cable and the end of the 120a fusible link box on the positive terminal.
    -The 100a fusible link at the front passes a visual inspection and reads about 0.05 ohms on my multimeter.
    -Prior to this issue arising the car had been sitting at airport parking for about 6 days and the car had been resetting the clock and MPG after being turned off, and sometimes instantly restarting after being turned off for about two weeks. From what I have seen on the forums the issues that existed before the car stopped having power have been attributed to faulty grounding or a bad 12v, however, the battery is good and as far as I can tell the grounding wire from the terminal is securely attached to the body.
    -My OBD2 reader is reporting 15.1 v when I have it jumpstarted and idling.
    -The car I jumpstart the Prius from does not need to be on for the Prius to come back to life, the leads simply needs to be connected to the terminals in both cars.
    -Trying to jumpstart from the trunk does nothing (which is to be expected if 12 volts are detected at the back but not at the front.

    Information that seems less prevalent but may be important to someone more knowledgeable than myself:
    -Some water has been pooling in the interior body paneling below the battery compartment.
    -The 12v was replaced in March of this year by the previous owner.
    -I have had this car for a few months but have put some serious mileage on it.
    -Whoever replaced the previous 12v apparently did not replace the hydrogen vent as I found it down by the spare tire. I immediately replace it when I noticed this about a week before this issue came up.

    My plan of attack is to continue to check relays, fuses, and circuit breakers between the front and back end according to wiring charts I obtained from this forum. Any advice or suggestions on where to look for blown fuses /lose wires / broken wires would be greatly appreciated!

    Many thanks,
    -Prius Bob
     
  2. Patrick Wong

    Patrick Wong DIY Enthusiast

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    The 120A MAIN fuse has blown or the cable between the 12V battery positive terminal and the dedicated jumpstart terminal is broken.
     
  3. BobThePrius

    BobThePrius Junior Member

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    The 120a fuse passes a visual and voltage test, I am currently looking for a break in the wire but nothing has turned up so far.
     
  4. Skibob

    Skibob Senior Member

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  5. sam spade 2

    sam spade 2 Senior Member

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    While your post implies that you checked it already................
    The most common cause of these symptoms is a bad connection at the OTHER end of the main negative cable, where it attaches to the frame or body.
    Go to the battery and measure for VOLTAGE from the negative battery terminal to the frame nearby.
    There should be none if the connection is good.
     
  6. BobThePrius

    BobThePrius Junior Member

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    I measured for from the negative terminal to the frame and got from 0.00v to 0.03 volts.
     
  7. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Sounds good.
     
  8. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Disconnect the 12V battery positive terminal. Measure resistance from the positive terminal connector to the dedicated positive jumpstart terminal at the main relay/fuse box. Use an extension wire to facilitate the measurement.
     
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  9. edthefox5

    edthefox5 Senior Member

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    Remove the big black wire off the top of the battery positive post by unclicking it and pulling it out. Measure the socket pin to ground for bat B+.

    That big black wire is the main B+ lead to the front fuse box.

    If you have it there you have blown the hardwire fusible link in the fuse box the 100 amp one under clear plastic. Usually blown from failed jump start. .

    Bitch to fix.

    if you have a leak the battery well is probably full of water too. Take the battery out there's a rubber drain plug in the bottom of the well. Remove that plug. If you don't the well will rust out.
    One poster has been driving around with bungee cords holding that battery in the car as the bottom of the well fell out from rust.

    I would also check for rodent damage too. take the cabin air filter out look for mice droppings. they get into the engine air cleaner box too so pop the cover off it and look.