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Car won't turn off after installing aftermarket head unit

Discussion in 'Gen 3 Prius Audio and Electronics' started by Tam Nguyen, Jan 22, 2019.

  1. Tam Nguyen

    Tam Nguyen New Member

    Joined:
    Jan 22, 2019
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    Location:
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    Vehicle:
    2010 Prius
    Model:
    II
    I replaced my factory head unit with a JVC KW-M740BT head unit recently. I am running into a problem where I have to manually turn on and off my head unit. When I turn off the car, the head unit stays on and all other electronic accessories stay on as well. When I manually power down the head unit, all the other electronic accessories turn off and then my Prius shuts down. What gives?

    Initially, I thought that I mixed up the battery/memory wire with the ignition/ACC wire, but I double checked and I did not mix them up. Why is my head unit preventing my car from turning off? Has anyone else run into this problem?
     
  2. Maarten28

    Maarten28 Active Member

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    Location:
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    Vehicle:
    2011 Prius
    Model:
    Three
    I would guess that there is some kind of connection between the always on 12V line and the switched 12V line that causes power to be fed to the car. Try unplugging the new head unit and see what happens.
     
  3. n23

    n23 Junior Member

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    Persona
    You may not have mixed them up, per a wiring diagram, but maybe the wiring diagram is wrong. My suggestion is to use a multimeter and check line voltage on all the wires with the ignition on and off. I'll bet your switched wire is mistakenly labeled and is actually a constant +12. Plan B, you could run a new switched wire from a known source that does turn off - the power feed to the cigarette lighter for instance.

    Lastly I've heard of circumstances where a large capacitor fed the stereo and amps after power was off. Do you have that equipment in the system too?
     
    HybridRide likes this.
  4. Dfreedom

    Dfreedom New Member

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    Vehicle:
    2010 Prius
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    N/A
    After installing the same after market radio system im having a very similar problem. The jvc radio wasn't shutting off on its own, so I manually shut it off. The car then beeped at me as I try to leave and wouldn't lock. When I went back to the prius the next morning the battery was dead.

    It seems that the prius power system will not shut off fully after the new radio installation.
    Has anyone solved this issue? Can I reset the computer somehow to work with the new radio system?
     
  5. zerotosixtysomeday

    zerotosixtysomeday New Member

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    2011 Prius
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    Did you ever solve this? My 2011 with my pioneer is having the exact same issue.
     
  6. Surfandstuffs

    Surfandstuffs New Member

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    Vehicle:
    2010 Prius
    Model:
    LE
    Bumping this thread as I had this issue with my 2010 Prius non-JBL HE and been scouring this forum, Reddit and YouTube for answers. Essentially, the issue for me was an aftermarket add-on that didn’t to be as such—found this out while on my 3 hr. Phone call with Crutchfield. I had an older 16 pin connector for an old iPhone/iPod added in my glove box (a Toyota product). According to Crutchfield info, this “dealer add-on” most likely offered at the time. Given I purchased the car (certified from a local dealership) I had no clue it was an add-on. In order to connect, this product has a t-harness connected to the 12 pin connector (unused with the wiring harness I purchased). Once I removed this product’s t-harness no issue and no problem with the car staying in accessory mode. I’ll try and make a post with some tags for others, but I’m guessing this is the culprit for many people when adding this to their 2010 (or older) Prius as the iPhone/iPod connector looks to be a factory install, but is connected behind the HE with zip ties and connector was wrapped with a electrical tape rather than ribbon like other connectors.