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P0AA6 Code / 526 Information Code--need help!

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by juliem, Jun 21, 2010.

  1. juliem

    juliem Junior Member

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    Okay folks, I need some help. I've got a 2006 Prius that was a model car--no problems at all--until it turned 4 years and 1 week old in April 2010. Then my aux battery died on 22 April, with just 31,583 miles on the car, and was replaced at Downtown Toyota in Oakland, CA. My dashboard lighted up after hours, and since my regular mechanic (Art's Automotive) was already closed for the evening, I had it towed to downtown Toyota. No huge deal, except for the cost of the battery/labor. :eek: The codes were: C2318, b1421, b1200, b1207, and b1271.

    4 weeks later, on 22 May, I pulled into my driveway, and 4 lights came on: the MIL, the VSC, the yellow ! inside the circle, and the Hybrid System Failure icon on the MFD.

    [​IMG]

    I turned the car off, and just like the Aux battery issue, I couldn't get it to restart. So I had it towed back to Downtown Toyota, assuming it was another battery issue. But when they ran the codes, it came up with the P0AA6/526 combination, and nothing more specific. Once they pulled the HOV (I think?) fuse, it cleared the codes and the car ran just fine. They spent a week driving it, testing it, and trying to get a more specific code to pop up, to no avail. The Prius tech said that it was the transaxle, the hybrid battery, or the inverter. But since these parts run $3500-$8000, they don't want to start replacing them one by one, which is completely understandable. They've never seen anything like this before, and opened a case with Toyota US (which doesn't have a record of any similar problems). DT Toyota told me that when it happened again, to drive straight to a Toyota dealer and get the codes pulled, or if I'm more than a mile or two away, to turn the car off, get towed in, and then pull the codes.

    So I've now had the car back for ~3 weeks, and just this morning--on 21 June--the same lights came back on. I was in Fresno, close to a dealer, so I drove to Michael Toyota, and they pulled the same code combination. They said that it was likely part of the TSB "MIL On/P3009/P0AA6" issue, handed me a copy of the TSB and a diagnostic report, and I drove back to Oakland and straight to DT Toyota. DT Toyota said that since my car is only showing the 526 code, and not 613, the TSB isn't applicable. They're going to keep it for a few days, and again try to see if they can get the code to pop back up.

    Now that this has happened twice, I'm trying to think if there's a pattern, and there are two similarities:

    • Both times, I'd left my car sitting for ~36-48 hours without driving it, then driven it short distances (less than 2 miles each way), turned it off, then back on, and then it threw the code within a few minutes.
    • My car seems to throw a code every four weeks! It keeps happening on the 22nd or 21st. Could there be some internal clock that's causing this? Last month, I'd jokingly said that I knew the car would be fine till the 22nd, and sure enough, it nearly was.
    If anyone here has had a similar experience, or has any suggestions on what this could be, or how to get my car to throw a more specific code, I'd love to hear it. Thanks!
     
  2. Patrick Wong

    Patrick Wong DIY Enthusiast

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    DTC P0AA6 means that the high voltage system has a ground fault. Normally that system is totally isolated from the car body. If a ground fault occurs, this DTC is logged.

    The bad news is that info code 526 means that the ground fault could be anywhere in the high voltage system, including the traction battery, the battery ECU, the cable that connects the battery to the inverter, the inverter, the transaxle, or the air conditioner compressor.

    Since this DTC is intermittent, my guess is that the traction battery ECU is at fault.

    BTW, there are a couple of TSBs relating to P0AA6. If info code 613 also had been logged, then T-SB-0306-08 suggests replacing the transaxle. If info code 614 was logged, TSB EG017-05 suggests replacing the inverter.

    As you know, once this DTC is logged, and you turn off the vehicle, it will not restart until the DTC is cleared. Therefore I think it is very reasonable for you to ask that your dealer take some action regarding replacing a relevant part, prior to turning the car back over to you - since this problem has happened twice and is well documented with your repair invoices. Good luck.
     
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  3. juliem

    juliem Junior Member

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    Thanks for the feedback Patrick! I wish the car would offer up an additional info code, but all it has given thus far is 526, not 613 or 614. Here's hoping that will change in the next couple days. This is the first I've heard about the traction battery ECU--I assume this is the computer that controls the hybrid/traction battery?
     
  4. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Hi Julie,

    The traction battery ECU keeps track of the battery state-of-charge and provides this info to the hybrid vehicle ECU so that the latter knows how much power to take from the battery when you are accelerating, and how much charging current the battery needs when under regen.

    The following list shows all possible trouble areas given info code 526. Since your car hasn't logged other info codes (which could range from 611 to 614) and the problem is intermittent, the question is which of those potential trouble areas could have an intermittent failure. Therefore, if info codes 611 - 614 do not appear while the car is being test driven at your dealer, I'd suggest that the traction battery ECU should be replaced so that at least they will have taken some positive action besides running up the odometer reading.



    Frame wire


    System main relay


    System main resistor


    HV battery assembly


    w/ motor compressor assembly


    Battery ECU


    HV transaxle assembly


    w/ converter inverter assembly


    Main battery cable


    Main battery cable No. 2


    Battery plug


    Frame wire No. 2
    Junction block assembly

     
  5. juliem

    juliem Junior Member

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    Thanks so much Patrick! My car has been sitting on the lot, undriven, since Monday afternoon, in an attempt to replicate that possible pattern. Here's hoping it'll offer up a more specific code when they power it on today. If not, I'll definitely mention the ECU.

    I forgot to mention this in the original post, and I don't know if it matters, but after my car coded on Monday, I wasn't able to use cruise control, and my Bluetooth was also disabled. Someone told me that the car turned off non-essential services when it had an error, so the loss of these services could have been due to that. But maybe not?
     
  6. vertex

    vertex Active Member

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    Take the car to Lucious Garage in San Francisco. They may be able to do a better job, at a much lower cost!
     
  7. Patrick Wong

    Patrick Wong DIY Enthusiast

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    OP's car is covered under hybrid system warranty, so no point in taking it to a non-Toyota repair locale.
     
  8. juliem

    juliem Junior Member

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    Yep, that's correct, thanks Patrick. Besides, I've been a faithful Art's Automotive customer for the past 4 years, so I'd rather take the car to them than Luscious Garage. But since this is a warranty issue, I think I have to stick with Toyota repair.
     
  9. Mike Dimmick

    Mike Dimmick Active Member

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    I've used Art's website to understand the Prius repeatedly, I think they know what they're doing. Their website was instrumental in my buying decision. In fact I reckon they have much more of a clue than the dealer - they have access to the service manuals, the diagnostic tester (as they specialize in Japanese cars) and by their own accounts appear to actually follow the diagnostic tree, plus use their own brains to think of other possible causes. The dealers often seem to just tell you that the most expensive part needs replacing without following up all the leads that Toyota engineering have flagged in the documentation.

    TSBs are basically special updates to the service manual flagging up common problems that have a known cause, usually with a design change that corrects the issue. The existence of a TSB that mentions a DTC does not invalidate the information in the manual! If the conditions for the TSB don't match, go to the normal diagnostic tree.

    There is an 29 step tree to resolve P0AA6 problems. If the fault is intermittent the on-board diagnostic software may not be able to narrow down the issue, so all the steps will have to be performed. The more specific INF codes simply allow some steps to be skipped as the OBD software has already ruled them out. The dealer should be following this tree and not wasting any more of your time (and their own shop space). They won't waste money on replacing parts unnecessarily if they actually follow the tree to determine which is the most likely cause first.
     
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  10. juliem

    juliem Junior Member

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    Thanks Mike! I'm heading to the dealer now to drop off the rental, and to see if they've had any luck with my car. I know they put in ~6 hours of diagnostic work on my car last month, and I'm assuming that they were working their way through the tree, but I'll be sure to check on that today. At this point, Toyota is refusing to replace anything until the problem can be duplicated and the source problem diagnosed.
     
  11. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Hi Julie,

    If you find that the root cause of your car's problem has not been identified, and this policy is repeated to you today, then I would suggest that you respond that your car clearly has a problem. This has been documented by the same DTC being retrieved twice by Toyota dealerships. It is not your fault that the problem is intermittent and that Toyota's diagnostics are incapable of identifying the root cause.

    Therefore, you are requesting that the dealer continue to pay for a rental vehicle while they work on your car, or else the dealer can demonstrate that the tech has thought about what component might be susceptible to an intermittent problem, and has replaced that component, so that component can be ruled out if you suffer a third occurrence of DTC P0AA6.

    It is not right for the dealer to return the car to you after you've experienced two serious failures, without any action being taken to remedy the underlying issue. Good luck.
     
  12. juliem

    juliem Junior Member

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    Hi all,

    Just heard from the dealer, and a local Toyota engineer gave them the green light to replace the hybrid battery. There's no confirmation that this was the problematic element, but Toyota and the dealer (and myself!) are hopefully this will fix the problem. Thank you for all of your ideas and suggestions!

    Patrick--thanks for the stern talking-to. (-: The dealer has been (surprisingly) great to deal with--very communicative and accommodating, so I have no complaints. Maybe I'm taking it too easy on them, but I can understand their hesitation when it comes to replacing such expensive parts. I understand that they'll get reimbursement from Toyota, but I'd rather them take the time to find out exactly what is wrong, especially since the car is drivable, even while coding.
     
  13. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Hi Julie,

    Thanks for the update. I'm glad to see that some action is being taken on your car.

    If the dealer is not far from your location, perhaps you might want to take a look at the old battery after it has been removed from the car and the case opened up. The tech needs to open up the case so that the traction battery ECU and the three system main relays can be swapped from the original battery case to the new case.

    If you do not see electrolyte leaking from a module to the metal battery case, then it is doubtful that the traction battery is the cause of the high voltage leak. Nevertheless I certainly would not argue if they want to install a new traction battery in your car. Good luck.
     
  14. juliem

    juliem Junior Member

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    Hi Patrick,

    The dealer is close, but I wasn't able to make it there in time to see the used battery. However, I asked the Prius tech, and he said that there wasn't any evidence of corrosion or leakage. So while I'm happy to have a new battery, I'm not at all convinced that was the cause of the problems. But hey, as you said, who am I to argue if Toyota wants to give me a new battery? I'll let y'all know if I start having problems again soon. If the pattern holds up, I'll code again on the 21st/22nd.
     
  15. juliem

    juliem Junior Member

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    The pattern has been broken! The lights popped up on the dash and MFD again last night, only 2 weeks after the last trip to the dealer. I knew replacing the hybrid battery was only an educated guess, so I wasn't too surprised by this turn of events, but it was a rather unpleasant surprise at 10:30pm. I turned the car off immediately, and this morning, after having it towed back to Toyota, the tech was finally able to get the mysterious code--613 (as well as the standard DTC P0AA6/info code 526)--which indicated a faulty transaxle. A replacement transmission has been ordered, and I should have the car back by Friday.

    Here's hoping that a new transmission will finally fix the car. If not, I'll start looking into lemon law, and deciding whether or not to take action. After spending a couple of weeks driving a new 2010 Prius, I'm pretty convinced that I like my older model better, especially since I have the CA HOV stickers.
     
  16. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Hi Julie,

    Well, this is very good news. As a Prius owner this is the closest that you can come to winning the California Lottery: new traction battery and new transaxle, at Toyota's expense.

    <Not sure why you would want to invoke the lemon law even if it were applicable to your situation: would you really be unhappy if every part of the hybrid system was eventually replaced on T's dime?>
     
  17. 2009Prius

    2009Prius A Wimpy DIYer

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    I didn't know the lemon law applies to old cars?

    Regarding the warranty repairs, is Toyota paying for the towing as well as the rental car?

    Could there be a quality/craftsmanship difference between the original factory installation and the dealer repair installation?
     
  18. juliem

    juliem Junior Member

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    @Patrick--Ha, I guess you're right, lucky me! ~8k worth of parts, and hours of labor, all on Toyota's dime! I'm just glad that it's (probably) resolved. If the car continues to code on a regular basis from here on out, then I'll look into lemon law. I do a lot of highway driving/traveling, and won't risk having the car code somewhere on I-5 or 99. But as long as it behaves, I'm happy to keep it for several more years. Especially while the Platinum warranty is in effect.

    @2009 Toyota is paying for the rental, and if I had paid for the tow out-of-pocket, they would reimburse that. Luckily, I have roadside/towing through my car insurance (21st Century). The tow truck driver knows me by sight now. /-:

    I can't imagine there would be a quality difference between the installations--if that were the case, we wouldn't be able to trust the dealer for any fixes, yes?

    And my car isn't that old--only 4 years and a few months! And since it's all still warrantied, I believe it's eligible for lemon law issues.
     
  19. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Hi Julie,

    In the (possibly likely) event that your car still logs this code after the transaxle is replaced, I hope that you know that you can still drive the car until you make the car IG-OFF. So, if this happens in an inconvenient place, continue driving and carry out your itinerary. When it is time to park, just leave the car READY, in P, and with the parking brake set (if you can find a safe place to park where you don't have to worry about the car being stolen.)

    The transaxle replacement is probably the biggest repair job that the dealer techs will do. I'm sure it will go well for you as that work is usually assigned to the best staff.
     
  20. juliem

    juliem Junior Member

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    @Patrick, Yep, I do know that--and actually drove from Fresno, CA to Oakland, CA (~170 miles) with the dash lit up last month. Even though I know its safe for me and the car, it's still a little nerve-wracking. And interestingly (at least to me), when the car coded, I lost use of both my bluetooth and cruise control. Made for a very long boring drive.