1. Attachments are working again! Check out this thread for more details and to report any other bugs.

P0A94-555 Want bench test rig

Discussion in 'Gen 2 Prius Technical Discussion' started by madman34, Jun 18, 2024.

  1. madman34

    madman34 MAD Scientist

    Joined:
    Mar 11, 2011
    3
    2
    0
    Location:
    Yucca, Arizona
    Vehicle:
    2008 Prius
    Model:
    ----USA----
    Greetings all,
    I am just the typical obsessed engineer rocket scientist, yes really, and when something stupid happens that should't have happened, I must find out why and fix it. Heres the issue and what I know so far and would like to get input on what to do. I have an 08 and an 09. The 09 is the subject of the anomoly. Car has 180k on her, never been messed with in any way, all maintenance done, HV battery replaced 2 years ago with OEM by previous owner, has operated flawlessly for the year I have owned her, never had my golden screwdriver to it. Car bought for and driven mostly by my girlfriend who has enjoyed the carefree experience. 2 weeks ago she took me to get a truck I had left at a job about 10 miles away, when suddenly and without warning at a stop sign we got the red triangle of death and christmas tree of failure. Car went into limp mode and fortunatly we were within site of the truck we were going after, my rollback tow truck ;-) when we shut car off she would not go into ready and only go into neutral, making it easy to put up on truck. At home, she registered the P0A94-555 to which i did all troubleshooting steps to the end result of replacing the inverter/converter with a salvage unit and this fixed the issue, girlfriend happy because the car runs again. Thats not good enough for me though, because this failure is just wrong because this unit in a gen 2 is known to be nearly bulletproof, so I must know what part failed and fix it. I dont have a spare prius to use as a test bed because I drive the 08 for work, so I wonder if anyone has had success getting the inverter to fire up on a work bench test be of any sort? If not, I would like to try to fabricate a jig that would satisfy the needs to make the boost converter to fire up, since this is the nature of the error code. Anyone got data on this?? Thanks.
     
    #1 madman34, Jun 18, 2024
    Meg&Bear likes this.
  2. ChapmanF

    ChapmanF Senior Member

    Joined:
    Mar 30, 2008
    24,902
    16,209
    0
    Location:
    Indiana, USA
    Vehicle:
    2010 Prius
    Model:
    IV
    Well, even if you never get any further, you've just shaken me out of a mistake I've been making for years.

    I've always seen the P0A94 fortune cookie "DC/DC converter ..." and thought "oh, that's about what Toyota calls the DC/DC converter, namely the one that takes the 202 V traction battery voltage down to 12 V for the car electronics."

    But sure enough, you're right, it's about the boost converter, the one that takes the 202 V battery voltage up to 500 for the motors. That's also a "DC/DC converter", of course, in the general sense, just not the one Toyota calls by that name.

    Serves me right for reading too much into the fortune cookie, seeing as I warn other people off doing that all the time. And it's a P0 code, meaning SAE chose the name, and Toyota's stuck with it, even though they use that name themselves for a different part of the car.

    It might be easier for you if the code really were about the 200-to-12 volt one; I think that has less complicated control signaling and might be easier to coax into operation on the bench.

    Have you looked over on openinverter.org?
     
    #2 ChapmanF, Jun 18, 2024
    douglasjre and Meg&Bear like this.
  3. rjparker

    rjparker Tu Humilde Sirviente

    Joined:
    Jun 6, 2008
    8,486
    5,050
    7
    Location:
    Texas Hill Country
    Vehicle:
    2012 Prius v wagon
    Model:
    Three
    Its not really known to be bulletproof, it does fail as you and many others have seen. Gen3s inverters fail more often and are still covered by Toyota. My gen3 also failed suddenly and without warning.

    Toyota does not share schematics on the inverter converter and most don’t care since used replacements are cheap.
     
    #3 rjparker, Jul 22, 2024
    Meg&Bear likes this.
  4. mr_guy_mann

    mr_guy_mann Senior Member

    Joined:
    Sep 3, 2020
    3,668
    1,714
    0
    Location:
    NJ-USA
    Vehicle:
    2006 Prius
    Model:
    Four
    I would just open up the inverter and poke around. Look for fried mosfets or diodes. The main assemblies are fairly modular.

    WeberAuto on youtube has pretty good overview of the whole system.

    Posted via the PriusChat mobile app.
     
    #4 mr_guy_mann, Jul 23, 2024
  5. ChapmanF

    ChapmanF Senior Member

    Joined:
    Mar 30, 2008
    24,902
    16,209
    0
    Location:
    Indiana, USA
    Vehicle:
    2010 Prius
    Model:
    IV
    Poke around for edumacation purposes, you mean?

    Fairly modular it may be, but I suspect getting it reassembled, with the right thermal interface materials in the right places applied the right way, could be non-trivial.
     
    #5 ChapmanF, Jul 23, 2024
  6. mr_guy_mann

    mr_guy_mann Senior Member

    Joined:
    Sep 3, 2020
    3,668
    1,714
    0
    Location:
    NJ-USA
    Vehicle:
    2006 Prius
    Model:
    Four
    If it's a bad inverter that causes codes, then no reason not to "disassemble to the point of failure".

    Posted via the PriusChat mobile app.
     
    #6 mr_guy_mann, Jul 25, 2024
(You must log in or sign up to post here.)