P0AA6 Code / 526 Information Code--need help!

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. 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.



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!

 

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?

 

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?

 

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.

 

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.

 

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.

 

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.

 

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.

 

@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.

 

@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.