Check engine light code P0A78 issue

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Anatoliy Merva, Mar 7, 2020.

  1. Anatoliy Merva

    Anatoliy Merva New Member

    Mar 7, 2020
    2013 Prius
    Hello, I have recently bought a Toyota Prius 2013 3rd Gen from a subsequent owner. Unfortunately it is salvage title.

    The owner has taken it to the dealer and they replaced the necessary parts, I have seen the paperwork for it and it checked out.

    I bought the car with that knowledge thinking that Toyota had taken care of the issue but recently the check engine light kicks in super randomly. I drove 520 miles without it going on and yesterday it came on multiple times within 100 miles or so. It was a hot day, I stopped the car let it cool down, after 70 miles it kicked in again. Car was running hot, the radiator fans weren’t blowing so I turned on the AC, I drove 200 miles until it kicked in again.
    When the the check engine light kicks in, you can feel a knock or a stall on the engine or inverter.
    I can drive over 20 miles without any funky smell or performance issues besides the car burning more gas using just the engine.

    I took it to Autozone for a code read
    “P0A78 Drive Motor ‘A’ inverter performance”

    I did a little of my own inspecting and diagnosing.
    -When the stall or kick in the engine/inverter happens, the light comes on. I go to display and EV or ECO mode are not present.
    - I unhooked the hybrid battery clip and removed a white wire on the fuse box.
    When I plugged the white wire back in, I heard a sound go off near the fuse box, hooked up the hybrid battery clip (Orange looking harness)
    The car wouldn’t even go on ready, panicking that I would have to get it towed. I did the wiring once more, the check engine light when off, car started and drove off.
    - I inspected the inverted coolant reservoir, it is just a few centimeters above the full, no turbulence when car is “Ready”
    -The radiator coolant reservoir is way over the full line, sometimes it goes very close to the gas cap when the check engine light is on.
    On the same note, I see the reservoir usually go with level on the full line.

    Is my inverter coolant pump failing?
    Does it have anything to do with the wiring?
    If my inverter shuts off and my car is only using the engine, am I safe to drive it?

    I am trying to do process of elimination but I am having a hard time even deciding on what to replace and where to start, what else should I check?

    Attached Files:

  2. bisco

    bisco cookie crumbler

    May 11, 2005
    2012 Prius Plug-in
    Plug-in Base
    ‘No turbulence when car is ready’

    Yep, but probably not the only problem

    You need tech stream