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P0AA6 & more! Seemingly out of nowhere...

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by maleko, Aug 3, 2019.

  1. maleko

    maleko Member

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    Hey guys, today I embark on the dreaded HV system failure troubleshooting process. I am not an expert, but I can definitely get things done. Would appreciate some support and input along the way. I have the P0AA6 with detail codes 526 and 612. A quick search later and I am planning to pull my hybrid battery for visual inspection today.

    Our 2008 Prius has somewhere around 175k on it and has not had an easy life. It hails from the hot and dry California / west coast of the U.S. and now lives in the incredibly humid and wet Florida. It gets driven hard by Prius standards and was in a major accident early in it's life. We have owned it since 2013 with minimal maintenance/common minor issues and no major issues to speak of. It does burn a bit too much oil for my liking but I check it weekly and it is no longer my primary commuter car so it is living a more relaxed life with my wife these days. It has a faulty combination meter / dash board and some other minor codes I have kept an eye on but were nothing major. It has definitely lost MPGs since the day we bought it, but I just attributed it to some loss of compression/oil burning and an aging HV battery. I have serviced it well and maintain my vehicles where it matters since owning it. I also have a mini VCI and Tech Stream for diagnostics.

    So yesterday I started the car as usual with the family loaded up to go-to a doctor's appointment and immediately got a warning across the MFD (touchscreen display) that just said PROBLEM with an (!) in a triangle. I shut the car off in the driveway and upon restarting it, it was immobilized. We had just driven it a day or two prior for an hour long car trip with no issues all the way home. I immediately pulled codes and got the following:

    20190802_145459.jpg 20190802_150904.jpg

    I am aware of the P1121 code and already have the part sitting on my shelf ready to swap in. I also had the inverter coolant pump fail and replaced that not too long ago as well. I don't suspect my coolant storage tank (P1151 is truly bad as this code only showed up after swapping out cooling system parts- I expect a better bleed may resolve the P1151 code. The P3193 code (out of fuel is my understanding) is likely from a month or two ago when my wife ran out of fuel on the highway and had to have our roadside assistance bring us fuel. I don't think I pulled codes after that incident until now so that makes sense to see it in the history but our Prius definitely has fuel in it currently so not sure why it is also marked as a current code. Based on this link here:

    07 Prius Codes C1259 C1310 P3018 | PriusChat

    codes C1259 and C1310 are byproducts of the root cause code P0AA6. According to this thread here:

    Error code B1421 | PriusChat

    code B1421 is a BS code with nearly no meaning as I have had that code hanging around since buying the car and our AC has been working normally the entire time we've owned the Prius. Additionally, the B1442 AC damper control code has been intermittent for some years now and just hasn't been a priority to fix with how busy I am all the time. I will likely do that repair when I replace the AC blower motor as it's bearings are getting squeaky and annoying now. And finally, code B1271 correlates directly to the faulty dashboard combination meter I referenced and has been a known issue to us for several years now.
     
  2. maleko

    maleko Member

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    So this morning I disconnected the 12V battery for 10 minutes or so and allowed everything to reset/clear, then fired the Prius up to still receive the yellow triangle with (!) and "PROBLEM" across the touch screen display. However, after a minute or two, I went to cycle the car off by pressing the power button with my foot still on the brake and it then fully powered up normally. Everything was working and no indicator or warning lights of any kind were active (the dash happened to be working this morning). For some reason my gas gauge was blinking on 1 pip as if it were on E. After letting it idle and charge for a few minutes, I power cycled it off and back on a few times with no new surprises. After I felt I could trust it enough for a quick 5 minute run to the gas station less than 2 miles from our house I headed for gas. Within that 2 mile trip my gas gauge instantly flipped from E to full 10 pips. I topped off the tank to be sure and it only took 1.75 gallons so my estimate of fuel level was indeed adequate. Got it back home, still no indications of any trouble. Debating whether or not it is worth tearing out the HV battery for visual inspection or if I should just continue to run it until I get the same code again. I really don't want my wife to get stranded, but she doesn't go far and we do have roadside assistance and family/friends in the area who can help out if it ever came to it.

    Is there any chance water getting in the front end from driving through puddles and/or soaked roads could have caused a misleading trouble code (ie water in the air compressor plug)?

    I don't have my splash shields on the underside of the engine bay (haven't for years) and never had issues driving in wet conditions before, but as I said, now we are in Florida where it rains daily, our street is pure potholes, and we have to drive through multiple large puddles to get in and out of our house/street daily.
     
  3. davecook89t

    davecook89t Senior Member

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    Did you see any sign of moisture in the area where the 12V battery resides when you disconnected the cable? Leaking seals around the hatch are common with these older Gen 2 cars. That may also be contributing to the shorting out of your HV battery with ground, which is what P0AA6-526 and P0AA6-612 indicate. You may not actually have to pull the HV battery out, just dry the area around the HV battery and fix the leaking seals. Not addressing this problem, if it exists, will probably lead to a worsening condition over time.
     
  4. maleko

    maleko Member

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    I did not see any obvious water intrusion in the rear hatch area today but I have in the past. In fact I'm pretty sure it does get wet sometimes due to the subfloor "carpeting" getting wet near the two corners by the taillights during wet periods. Never caused any issues previously however and I have not managed to pinpoint the exact point of ingress.
     
  5. maleko

    maleko Member

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    I think it may all make sense now. Our Prius used to always be parked on flat ground but now gets backed in up a decently steep driveway. Previously the water stayed in the rear and exited but now it seeps forward into the battery zone. @davecook89t may have hit the nail on the head. Check out these pics here:

    20190803_164301.jpg 20190803_164309.jpg 20190803_164330.jpg 20190803_164350.jpg
     
    #5 maleko, Aug 3, 2019
    Last edited: Aug 3, 2019
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  6. davecook89t

    davecook89t Senior Member

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    If not the seals around the hatch, it may be the seam that runs along the side of the roof. I believe others have found issues in that area as well, or as you speculate, it may be coming through the taillights. If it's a slow leak, it might be hard to isolate, especially as you are getting rain every day, and if this has been a problem for a while, damage to the HV battery's circuits has probably already been done, sorry to say. You'll find plenty of pictures of corrosion on the pins of HV battery's ECU on this site, probably due to water intrusion in most cases. It may not be pretty, but I would probably try to run a bead of silicone sealant around the taillights and any other areas where water might be intruding, especially if you clean up the HV battery and its circuitry. You definitely wouldn't want to have it happen all over again.
     
  7. davecook89t

    davecook89t Senior Member

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    :(, Well now that you've started by pulling off some of the panels you might as well keep going to see how bad it has gotten. Our 2007 has a similar history to yours (originally came from Cali, but now spends its summers in the hot, humid, rainy Northeast). Additionally, it is parked facing downhill in our driveway, meaning that any water coming through the hatch would run toward the HV battery. I think I'll go out and check it right now.:unsure:
     
  8. maleko

    maleko Member

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    (Also forgot to mention that in Cali it stayed parked under a covered parking area, so 80% of the rain we got stayed off most of the car. The only time the water intrusions were really noticed were after running errands around the city all day on rainy days or on our cross country road trip or other long excursions, etc. Here in Florida it is exposed completely and not under any kind of cover. We have been living here in FL for about 1 year exactly. This summer has been especially rainy compared to last summer when we first arrived.)

    I found the source. Don't mind the atrocious state of the seat where our daughter has spilled milk and juice over the years... I've been meaning to clean it. See here:
    20190803_170009.jpg 20190803_172621.jpg 20190803_172612.jpg 20190803_172600.jpg
     
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  9. davecook89t

    davecook89t Senior Member

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    Aha, the roof seam! That seems to be the problem more often than not. I wonder why.
     
  10. maleko

    maleko Member

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    Well in our car's case, it had the entire rear driver's side quarter replaced and grafted on from another donor vehicle. We bought the car like this with the rear quarter wheel well dent but didn't realize the extent of the reconstruction and repair until after it was too late. All in all though it's been a pretty damn reliable car that we have already put about 100k miles on in about 6 years now.

    Check out the cracks where the graft was done:
    20190803_174226.jpg 20190803_174244.jpg 20190803_174340.jpg
     
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  11. maleko

    maleko Member

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    Almost done prepping this Frankenstein nightmare of a Prius I own. Been digging out Bondo and identifying all points of ingress in preparation for sealing them all up. It's not going to be pretty...

    20190803_195030.jpg 20190803_195044.jpg 20190803_195158.jpg 20190803_195223.jpg 20190803_195247.jpg 20190803_195357.jpg 20190803_195417.jpg 20190803_195433.jpg
     
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  12. Patrick Wong

    Patrick Wong DIY Enthusiast

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    It will certainly help if you can prevent further moisture from entering the hatch area.

    As previously mentioned, P0AA6 with info code 612 means that you have a high voltage ground fault in the high voltage traction battery area. The most likely cause is one or more of the 28 battery modules leaking electrolyte to the battery case. That forms a conductive path to body ground, hence resulting in the ground fault.
     
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  13. maleko

    maleko Member

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    My headliner, rear quarter pillar, driver's side rear seat back and bottom were all wet today from sitting in the rain for several days in a row now. The seat back/bottom sit right up against the casement for the HV battery and the path of ingress had all the sound deadening insulation that backs the interior plastics wet too along with mild puddles forming under the HV battery itself. Additionally that side and path the water was entering through and settling into the valleys of is also the same path a main umbilical from the HV is routed as well as the primary HV cable exit from the HV battery pack. All things considered and based on my specific circumstances, I believe the water intrusion was likely my cause of ground fault. Once I eliminate that issue, if the same problem comes back I will surely be examining my battery much closer but for now, all signs point to water getting in where it shouldn't.
     
  14. maleko

    maleko Member

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    Like I said, it's not pretty, but it's got a rubberized, 15 year type roof sealant (I happened to already have some on hand from recent roof repairs to the house.) Lol.

    20190804_165636.jpg 20190804_162655.jpg 20190804_164826.jpg 20190804_164832.jpg 20190804_164857.jpg
     
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  15. maleko

    maleko Member

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    And since I've got it in the garage for work, I just couldn't resist checking out the HV pack:

    20190804_182752.jpg 20190804_182817.jpg 20190804_182904.jpg 20190804_182910.jpg 20190804_182917.jpg 20190804_183014.jpg 20190804_183023.jpg 20190804_183027.jpg 20190804_183031.jpg 20190804_183035.jpg
     
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  16. Patrick Wong

    Patrick Wong DIY Enthusiast

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    It doesn't look too great. Every terminal where you see corrosion is a possible candidate for electrolyte seeping out of the module and causing the ground fault.

    And of course it doesn't help for you to have a little pool of water in the hatch area.
     
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  17. maleko

    maleko Member

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    2 questions:

    1.) Can you recommend a *new* and *quality* pack I can purchase and install that will retain some amount of warranty?

    2.) Can you direct me to a pack teardown video or "how-to"? This is my first time and I'm just looking to clean up while exploring so I have some practice when it really comes time and so I don't light myself up with 130VDC lol.
     
  18. Patrick Wong

    Patrick Wong DIY Enthusiast

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    1) Buy a new battery from a Toyota dealer parts dept. The warranty will only be 1 year if you DIY install, but warranty is not really needed on a new Toyota battery.
    2) techinfo.toyota.com is where you can get the repair manual and safety info.

    I assume you removed the orange traction battery interlock?

    Now that you have the battery open, use your digital multimeter set to measure volts. Attach the negative meter probe to the sheet metal battery case. With the positive meter probe, measure voltage starting from the module closest to the battery ECU. If you measure any voltage, you have a ground fault somewhere. Then move around, measuring voltage from one module to the next to see how the voltage fluctuates. When you get to the point where you measure a very low voltage, that is the source of your ground fault. However if there is more than one ground fault then the measurements might get weird as you move around.
     
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  19. maleko

    maleko Member

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    With my negative probe on the bottom of the battery case going down the line with my positive probe touching each modules terminal I get anywhere from 2 to 9 volts DC on my multimeter.

    EDIT:

    After removing all of the nuts and disconnecting the modules from each other so that each one is individual I was able to isolate the end most model opposite of the battery control unit computer. It appears to be leaking 3 to 4 volts to ground. That also seems to coincide with the leak that appears visible at the bottom on that end.
     
    #19 maleko, Aug 4, 2019
    Last edited: Aug 4, 2019
  20. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Each module produces around 8VDC, so you may have many ground fault issues with the modules. Another test would be to remove the bus bar on one side so that the modules are isolated from each other. Then measure voltage again. Any module where you can measure voltage to the sheet metal ground has an electrolyte leak.

    If you do this, be careful to correctly torque the bus bar nuts, the tightening torque is only 4 ft.-lb. There are several posts from overzealous owners who excessively tightened the nuts and a module stud sheared off. You don't need that to happen to you.
     
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