Newly installed hybrid battery no longer functioning after failed test drive

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Brenn, Jun 6, 2026 at 3:27 PM.

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  1. Brenn

    Brenn New Member

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    Hello! FYI I’m new to this forum and to forum etiquette, but I searched around for a while and couldn’t find any answers for my specific problem, so here I am!

    Here’s the background info: I’ve got a 2008 Prius around 270k miles that my sister used to drive. The hybrid battery died while she was using it, and it sat dead for about a year. I’ve recently starting fixing it up, and so far I’ve replaced the old hybrid battery with a refurbished one (which includes a good warranty), and also replaced the old 12v battery with a brand new AGM one. After making those two fixes, the car would start but I would be stuck in park, unable to go anywhere. I was stuck with this problem for a few days, until last night I had an epiphany, and remembered that there was a white ground wire in the hybrid battery ECU that wasn’t connected. I connected that, and at last, the car started and I was able to go into gear!

    Here’s my current problem: So I took it on a test drive to let the systems wake up and calibrate, and almost immediately the red triangle of death appeared, but I kept driving since I read somewhere that warning lights usually come on during a test drive after installing a new hybrid battery. I made it about a half mile before the MPH number on the dash disappeared, and at the same time, the center screen’s display of power flowing through the car went blank and all power flow stopped. When that happened, the car slowed to a halt and turned off. The car will still turn on, but I can no longer go into gear, and it seems that the hybrid battery doesn’t want to come on. The orange safety plug is most definitely in place.

    Here’s what I know: The 12v battery is doing fine, I’ve tested the resting voltage and the voltage while the car is running, and all is well. I haven’t tried to get any codes, because I’m worried that I’ll drain the 12v battery. And I’m also not sure if the scanner I even got can get exact codes. I think the hybrid battery is running into some issue that won’t let it turn on all the way.
    I have the Innova FixAssist Wireless Bluetooth OBD2 Code Reader 3210RS

    Should I just bite the bullet and get it towed to the shop or is this something I can fix relatively easily?

    Thanks to those of you who take the time to read and reply!
     
    #1 Brenn, Jun 6, 2026 at 3:27 PM
  2. JC91006

    JC91006 Senior Member

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    I'm not sure where you read the part "the red triangle sometimes turns on after hybrid battery change". If you read that, it means there is a problem. Not that things will go back to normal.

    Refurbished batteries are the worst, hopefully you can still return it before your headache really begins. You're better off buying a lightly used battery from a wrecking yard, than any refurbished product. Refurbished items can be made from batteries as old as 1999, which is 27 years ago. There is no industry standard on how people refurbish a battery.

    I can't really think of a reason why the car would run down all it's power, but I suggest you read the codes so it can give you some idea of where the computer thinks the problems at.
     
    #2 JC91006, Jun 7, 2026 at 3:53 AM
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  3. ChapmanF

    ChapmanF Senior Member

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    It sounds to me as if the car's DC/DC converter shut down for some reason during your test drive, and you continued driving until the 12-volt battery was deeply discharged.

    In that case, worrying now about reading codes because it might discharge the 12-volt battery is kind of beside the point. You may need to recharge the 12-volt battery for several hours, and then see if you can read any codes. (They may have been lost with the loss of 12-volt power, requiring you to try again to power up or drive the car and see what codes come back.

    If you can retrace your steps to whatever internet sources gave you that information and you're able to leave comments there, you might be able to save other people some similar bad experiences in the future.
     
    #3 ChapmanF, Jun 7, 2026 at 8:32 AM
  4. Tombukt2

    Tombukt2 Senior Member

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    Let's put the thing on a charger and get the codes out of the silly thing. Then you have somewhere to go.
     
    #4 Tombukt2, Jun 7, 2026 at 9:40 AM
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