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Where do go from here, think I have a dead HV battery?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by MountWeasel, May 18, 2021.

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  1. MountWeasel

    MountWeasel Junior Member

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    To make a long story short:
    My daughter's 04 Prius won't start, and shows the 5 squares on the speedometer, then shuts off. 12v battery appears to be OK, MFD lights up in acc mode, but code reader won't connect to show codes.

    Problem is most likely self-induced, little bit of history:
    I removed the inverter reservoir to change a broken AC hose, apparently didn't get the O ring installed correctly, started leaking shortly afterwards. Daughter took the car to Houston anyways, and I drove down the next weekend and installed a new O ring which stopped the leak. However, the red triangle of death showed up next day after I had left. (maybe I didn't get all of the air bled out of the inverter coolant system, btw, the inverter coolant pump was changed last year) Autozone checked the codes, said it was just a bad O2 sensor (this was an old code), so she kept driving it. Car has now shut of completely, assuming HV battery is dead. I drove to Houston Sunday and brought the car back on a trailer, (it's really hard to load it on a car trailer when you can't put it into neutral)

    Where do I go from here?
    1. Is it normal to be unable to connect with a code reader if the HV batter is dead?
    2. Can I charge the HV battery in the car, or do I need to remove and disassemble it to charge each cell individually?
    3. Am I missing something simple, what else can I check
     
  2. bisco

    bisco cookie crumbler

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    too bad you didn't know about hometown hybrids in houston, good people.

    what code reader? you really need tech stream (toyota)

    you can charge it in the car, but you have to open it up to connect the permanent pigtail

    how many miles on her?
     
  3. TMR-JWAP

    TMR-JWAP Senior Member

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    The HV battery has zero input on whether the dashboard comes to life or not. The 12v system alone is what boots up the aux systems.

    The only time I've seen the squares on the gear indicator was when the 12v supply was actually around 9.5 volts. First thing I would do is check the 12v reading at the underhood jump point, as that is the location that really matters. The jump point is where the (+) 12v battery cable connects to the fusebox and is then distributed to the rest of the fuse box via all the fusible links inside the white plastic box with the clear cover. If the jump point is good, verify each of the fusible links under the clear cover and verify all fuses.

    The other possibility I can think of right off the top of my head is a problem with the power source ecu.
     
  4. MountWeasel

    MountWeasel Junior Member

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    Thanks for the advice, really appreciate it. I don't have Techstream, but I've used my bi-directional Autel MD802 to pull and clear codes from this car many times in the past, so I don't think that's the issue.

    Is there a write up somewhere on how to charge the battery in the car? I'm not opposed to pulling the battery, but having done it twice already, I don't want to if I don't have to.

    About three years ago, the odometer stopped at 299,999, so I'm guessing around 350k. But that's probably not too relevant, since I've changed the engine/transmission once and HV battery twice.
     
  5. MountWeasel

    MountWeasel Junior Member

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    Thanks for the response, I may have been somewhat unclear in my original post. The MFD (in the middle of the dash) works fine in acc mode (start button without touching the brake) but if you step on the brake and try to start the car, the speedometer/gear indicator flashes on very briefly, then displays 5 squares, while the MFD never lights up. Other posts I've read say that's classic inverter coolant pump symptoms. Since I just re-installed the inverter cooler reservoir, I'm looking in that direction.
    The 12V battery shows 13.6 Volts at the underhood jump point, but I haven't figured out how to check the HV battery voltage yet.

    What's the easiest way to check HV battery voltage? I know I could remove the inverter cover, and check the voltage at the DC input to the inverter, but I'd really like to check it as close to the HV battery as possible.
     
  6. mr_guy_mann

    mr_guy_mann Senior Member

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    No- leave the inverter alone. Even if you took the HV battery out of the car, the dash should power up normally when you press the power button twice (ignition ON - not Ready mode).

    I would get a voltage reading on the fuses that should be powered up in Ready mode when you try to ready up (such as the AM2 fuse). Might try unplugging the inverter water pump and see if that changes anything.

    Posted via the PriusChat mobile app.
     
  7. dolj

    dolj Senior Member

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    That would be with the car in IG-ON or READY. You need to measure it after the car has been off for at least two hours. Additionally, it is also good to measure it under load which can also be done with the car off and switching the headlight on to high beam for 5 - 10 min. If the voltage does not settle to something above 10.5V you need to replace the 12V battery,
     
  8. TMR-JWAP

    TMR-JWAP Senior Member

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    The AM2 fuse should be a 15 amp fuse. Often, if the ICWP is failing and draws a large current, it blows this fuse and totally kills the car. BUT, it doesn't always fail hard enough to draw that much current, so it is possible it's drawing a significant current and drawing voltage down, but not enough to blow the fuse. Directly above and slightly toward the passenger side of the underhood fuse box is a single wire connector plug. That plug is in the power wire for the ICWS. Disconnect that plug to remove the ICWS from the circuit and see what happens. If no changes, then the ICWS is not the problem.

    Of course, if someone slammed a 30 amp fuse in AM2 position or something, that could be an issue also.
     
  9. bisco

    bisco cookie crumbler

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    look up 'hybridautomotive' to see their prolong charger system. plenty of threads here as well.
     
  10. MountWeasel

    MountWeasel Junior Member

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    Thanks for the sage advice, sounds like I’m barking up the wrong tree worrying about the HV battery at this point. I’ll unplug the inverter water pump tonight and see what happens. I’ll also test the battery to see if it’s ok.
     
  11. bisco

    bisco cookie crumbler

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    you're welcome
     
  12. MountWeasel

    MountWeasel Junior Member

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    Thanks for the advice, it was absolutely correct. Unplugged the ICWP, no change. Found AM2 fuse was blown, replaced it and things started working again. Plugged in the ICWP and the fuse didn’t blow, but didn’t take long to figure out the cause of the problem. After 3-4 minutes of looking around, smoke started pouring out of the ICWP. I’m thinking that maybe the missing coolant reservoir o ring got sucked into the ICWP and locked it up. Still shows red triangle and all warning lights, so I’ll get my code reader and keep looking around for other issues. You just saved me untold hours of wild goose chasing with your advice.
     
  13. dolj

    dolj Senior Member

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    You are not very clear on the status of the ICWP. Does it appear to be working? The smoke suggests not. So then, have you replaced the ICWP. If so, what is still causing problems that you feel the need to "get my code reader and keep looking around"?
     
  14. MountWeasel

    MountWeasel Junior Member

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    ICWP appears dead/locked up, got a new one coming. Still have red triangle, abs, check engine, vsc, and red car exclamation in the mfd, so I assume there are still some issues remaining.