Is it safe to drive an 07 Prius with P0AA6 code (Voltage Isolation Fault) due to a bad transmission?

Discussion in 'Gen 2 Prius Main Forum' started by Jesse Goldman, Jul 10, 2021.

  1. Jesse Goldman

    Jesse Goldman New Member

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    2007 Prius
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    Five
    For about a week I have been getting p0AA6 code from my OBD2 , took it to the Toyota Dealership and they also confirmed p0AA6 code, but did not give me a subcode other than 526 for some reason and I already took the car back. They said it needs a new Transaxle. On the printed report they gave me it says:

    "VERIFIED CUSTOMERS CONCERN RETRIEVED CODE P0AA6 WITH THE DETAIL CODE 526 FOUND TSB PERTAINING TO INTERNAL TRANSAXLE FAILURE OF THE VOLTAGE SYSTEM RAN TEST PLAN VERIFIED INTERNAL FAILURE RECOMMENDED TO START WITH KNOWN FAILURE OF TRANSAXLE AND RECONFIRM NORMAL OPERATION"


    Anyway is it safe to drive it for now, if the Transmission is really the cause of the issue? I have an appointment with a few other mechanics next week to get second opinions and to see if someone can install a used Transaxle. I'm just driving to work which is down the street and maybe around town and to the mechanics, nowhere too far. But I heard a high voltage leak can be dangerous?
     
  2. ChapmanF

    ChapmanF Senior Member

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    If this is a new thread about the same issue you raised here, it remains true that "due to a bad transmission" in your thread title is premature until a second INF code shows up (or equivalent further diagnosis is done).

    Once the second subcode shows up, depending on what it is, then you'll know whether it's "due to transaxle failure" or "due to battery failure" or "due to inverter failure" or "due to air conditioner failure" or "due to wiring failure", and from there it will be clearer what repair is needed.

    The car will generally allow you to do some driving, though you may have to reset the code to get it started again. Safe? There's judgment involved. Good idea to get the problem taken care of soon.

    On the other hand, jumping into a repair, before knowing what to repair, might be too soon.
     
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  3. Jesse Goldman

    Jesse Goldman New Member

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    Thanks for the reply. Yes this thread is about the same issue and i posted this yesterday, but I guess it only now got approved because i'm a new user. And yes I have been clearing the codes with an OBD2 to keep it driving. Yeah I didnt know that it could take a while for the second detail code to come up, now I feel i kinda wasted my $135 at the dealer since it's still not for sure the transmission. I wonder if they would let me take it in again to get checked for the second code without charging me again, ill have to call and ask. I have an appointment with another mechanic next week to get a second opinion, hopefully they also have the equipment to check for subcodes and can confirm whether or not it's the transmission, since i'd rather not take it back to the dealership.
     
    #3 Jesse Goldman, Jul 10, 2021
    Last edited: Jul 10, 2021
  4. ChapmanF

    ChapmanF Senior Member

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    If you have a way of clearing codes, you can also look for old threads on a way you can do some location of the leak yourself through a sequence of steps:

    If the code returns after some time with the car only ON, the leak is in the battery.

    If the code doesn't return until you make the car READY, the leak is in the frame wire or inverter.

    If the code doesn't return until you shift out of Park, the leak is in the transaxle.

    If the code doesn't return until you turn on A/C, the leak is in the A/C.

    Those are more or less the same steps the ECU is doing for you when it has already logged the 526 subcode and is deciding what second subcode to log.

    There are some OBD2 readers (other than Techstream) that also can read the subcodes, or at least can be taught to read them. There should be some Gen 2 Prius PID definitions findable on the net that include the locations of the subcodes.

    Repeatedly clearing the codes to keep driving might be part of why the dealer only saw the 526. Clearing the codes of course takes things back to square one, and then the car has to re-detect first that there is a leak (and set the 526), and then in a later drive cycle see that it has set 526 and do the extra work to set the second code.
     
  5. Jesse Goldman

    Jesse Goldman New Member

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    Interesting! The code seems to pop up kinda randomly though. Usually it pops up whole driving I would say. But sometimes I'll drive error free for a day, then turn it off. Then the next day I turn it on and it has the code. My sister said she got it once immediately after putting on her turn signal while driving. I don't think the A/C has ever triggered it and I don't think I've gotten it when the car was only ON and not in Ready mode. So am I basically wasting my time taking it to mechanics without having that second subcode? Will any mechanic be able to pinpoint the issue without it or no?
     
  6. Jesse Goldman

    Jesse Goldman New Member

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    Also, if we assume it is the Transaxle that's failing. How bad is it to keep driving the car with a bad Transaxle? Could other rpartd be damaged int he process or is it fine? I think I read somewhere it could damage the inverter if you drive with a bad Transaxle?
     
  7. ChapmanF

    ChapmanF Senior Member

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    I don't know that I've seen a specific report of that, but it stands to reason that it could be possible.

    If you never manage to catch it with that second subcode, then your mechanic can just follow through the whole "P0AA6 with only 526" troubleshooting section of the repair manual, which will involve taking a bunch of things apart and testing them with a megger. Here, "any mechanic" might mean "any mechanic comfortable with hybrids", because others might just say "high voltage system? megger? nope, not me."

    Even when the second subcode is available, a good mechanic will still work through the troubleshooting steps for that code, which will still involve some megger testing to confirm what's going on. What's good about the second code is that it lets you focus that testing on the identified one out of like five possible areas, so it saves you 80% of the troubleshooting work.
     
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