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    IDrivePrymaat New Member

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    2005 Prius. Manufacture date Dec 2004. 40200 miles. Has had 50P ECM Reprogram and 60C steering shaft. 5k service was done just Friday, 2/1. Drove normally over the weekend. Filled up on Sunday & drove to and from super bowl party after that.

    Unusually cold for here this a.m. (40-45F). Started normally. Proceeded about 1 mi downhill to red light; noticed battery full at bottom of hill. Got a BEEP, red exclamation point, check engine, + "PROBLEM" on MFD. Restarted car; same lights. Was able to turn right and go into gas station; seemed to run normally. Turned off and reseated gas cap (did not seem obviously loose). Turned on: exclamation point, check engine, + red exclamation car (hybrid malfunction) on MFD. Consulted manual ("Take to dealer immediately") and called home about a ride from the dealer; got a suggestion to make sure it didn't blow all its oil out of a mis-seated filter (happened to us on another vehicle!). Turned off, checked oil (slightly overfull), turned on: no abnormal lights.

    Called dealer. They suggested since the lights went off, I could drive it there, but it should be checked. Drove there uneventfully. They hooked up the computer, saying "probably the gas cap," then "Huh, I've never seen that before: DC/DC converter malfunction." I left it with them for a thorough checkout.

    They called a few hours later and said apparently I'm not the first; the Toyota database said to replace a computer with an updated version. They said it'd be under the hybrid warranty and ready tomorrow.

    I asked for the code: P0A78. From a little light googling, this seems to be related to TSB 02505, which seems to suggest an inverter replacement :eek: rather than ECU. Any thoughts? I suppose it's possible there are other codes they didn't read to me.
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    bwilson4web 03 and 10 Prius

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    This is the three restarts, clears the error indicators and quite normal.

    I wouldn't worry since they probably updated the hybrid ECU software. This computer controls the inverter and a problem could cause the inverter to misbehave. If the inverter had failed, the car would have been inert. Enjoy!

    Bob Wilson
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    IDrivePrymaat New Member

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    Yeah, I understand: I restarted 3 times and the error condition was no longer present, so the lights didn't come on anymore.

    I guess my real question is what's the link between P0A78 and an ECU replacement? Is there a TSB other than 02505 (sorry I typo'd that earlier) that I'm not seeing?
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    qbee42 My other car is a boat

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    It doesn't sound like an ECU replacement. It sounds more like they updated the firmware on the ECU, but I don't know that from the code.

    Tom
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    hobbit Senior Member

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    There are a ton of P0A78 codes; you have to get the *subcode*
    that hopefully their scantool picked up also.


    .
    Have them do a real point diagnosis.
    .
    _H*
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    IDrivePrymaat New Member

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    Well, I've got the car back, and the sheet has some different information than they had given me on the phone:

    CODE P0A94 INVERTER MALFUNCTION
    REPLACED HYBRID ECU PER TSB EG058-06

    Still no subcodes, but P0A94's been seen here before. Not sure if I actually had both P0A94 and P0A78 or what.

    The TSB was discussed here also. This implies that my subcode was 588 since they decided this TSB applied. Definitely looks like a replacement rather than just a firmware update.

    Someone over on the yahoo group had both P0A94 and P0A78, and had the ECU replaced.

    My charge was $662.03 to the hybrid warranty. Hope that's the last I hear of it, or if not, that recurrences also fall within the warranty period!
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    hobbit Senior Member

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    So evidently there was nothing wrong with your inverter at all.
    Well, we can hope that remains true, anyways -- if they
    misdiagnosed and there *is* a developing or intermittent
    problem in the inverter, you'll be back in there..
    .
    _H*
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    GreenLady New Member

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    HEY! Almost the exact same thing happened to me today!! The car was sitting in the garage and I heard some faint and anemic honking sounds from the car. I thought it was the alarm. I unlocked the car and tried to start it, but I got a bunch of warning lights (inclding the "red triangle of death". I pushed the start button a few times turning the car on and off and got the strange warning lights a few times, but then it finally started normally. Really weird.

    Does this sound like the same thing? Do you all recommend I take it in to the dealer (and show them this thread)?
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    IDrivePrymaat New Member

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    Yup!

    Yeah, and quite possibly not under my own power either. :eek:

    I'll hope for the ECU having actually been the problem.
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    IDrivePrymaat New Member

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    Does not sound that similar to me, except for the part where several warning lights were lit.

    I'm glad I took mine to get the code read, despite my initial sense that it was probably a loose gas cap. I'll do the same thing in the future, especially for sure while it's still under the hybrid warranty.
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    GreenLady New Member

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    Hmmm. Well I did talk to a service manager at a dealer, and he seemed to think the battery had gotten drained somehow. He suggested driving around for a while to re charge the battery and to call them back if it happens again. :confused:
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    IDrivePrymaat New Member

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    Guess what! No such luck. It happened again, except that it did not clear after 4 reboots. :eek: I was on the freeway right at the exit for a toyota dealer, so I did get there on my own power. Dropped off the key & form for them to pull the codes in the morning. Unfortunately it's my least fav dealer in the area, but I guess I can't be too choosy when it's putting up hybrid system errors where the manual says take it to a dealer immediately. I have a feeling I'm joining the inverter replacement club.
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    Patrick Wong DIY Enthusiast

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    Yes, this sounds likely...or less likely, you might become one of the few 2G owners in the Prius transaxle replacement club.

    Your initial post mentioned TSB EG025-05. In case this turns out to be relevant, I've attached the file.

    Which dealer is doing the warranty repair? The good news is that the inverter is covered under the very lengthy CA emissions warranty, 15 yr/150K miles. If the transaxle, that's covered under the 5 yr/60K powertrain warranty.

    Attached Files:

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    IDrivePrymaat New Member

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    Thanks for the file!

    It's at Toyota of Pasadena. I had a less-than-pleasant experience with their service manager at the 30000 service and had been going the extra distance to Longo since then. I took it to Longo for that warranty service about a month ago; since the error messages cleared and it had just been there for a service 3 days prior, I thought it was worth driving it down there. With the lights staying on, I did not want to ignore them and keep driving. So, here's Pasadena's chance to change my mind. They should just be opening up about now, so hopefully I'll know some codes before long.
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    galaxee mostly benevolent

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    if it's a dc/dc converter malfunction, that's an inverter replacement. that will be covered under the hybrid warranty.

    see if they won't give you the codes (and subcodes) and post them up here.
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    IDrivePrymaat New Member

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    P0A93. I'm getting a new water pump under powertrain warranty. Is my inverter failing piece by piece? :confused:

    I guess I should have started a new topic.
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    Patrick Wong DIY Enthusiast

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    Yes, this makes sense and is a known problem. I've attached the relevant TSB.

    The good news is that you immediately drove to the dealer so the inverter should not have been damaged by lack of cooling. However I wonder why this happened so soon after the hybrid vehicle ECU was replaced. Had the water pump failed back in early February? If you have mostly been taking short trips, it is possible that you could drive without trouble lights appearing even with a failed inverter water pump.

    You only have 40K miles on your car...it might benefit higher mileage Prius to have a preventive replacement of the inverter water pump rather than wait for it to fail.

    Attached Files:

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    bwilson4web 03 and 10 Prius

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    Speculation on my part but I'm wondering if there is any of the "jelled" coolant in the loop that Hobbit saw in his disassembled inverter coolant loop?

    Also, I wonder if this might be a 'failure to bleed properly' symptom too?

    Pure speculation but unlikely to tell at this point. If you get the old part, send me a PM and we may want to do some further analysis.

    Bob Wilson
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    Patrick Wong DIY Enthusiast

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    Hi Bob,

    A clogged coolant loop is possible. If true, we will see another post from IDrivePrymaat next week, saying that s/he again has a Christmas tree display. With 40K miles, it seems unlikely that the SLLC inverter coolant had been previously serviced (unless IDrivePrymaat fell victim to an aggressive service writer in the recent past) so air in the system should not be a problem.

    Now that the pump is being replaced, fresh SLLC will be installed. Maybe this will help remove any clogging that currently exists.
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    IDrivePrymaat New Member

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    I take mostly shortish but not microscopic trips (11mi/30min partially in traffic, partially at fwy speeds), but I can think of at least one that was more like 30mi/1h each way in traffic since the Feb. ECU replacement. I live on a foothill and I work on a different foothill, so this prius goes up and down more than some. I get full green battery going down with some regularity. I have wondered at times about side effects from this lifestyle.

    The idea of one inverter-related failure per calendar month is not really what I am looking for. :(

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