2005 Prius P0AA6 VERY intermittent

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Bornloser, May 15, 2017.

  1. Bornloser

    Bornloser Junior Member

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    I have a 2005 Prius with about 160K miles. I replaced several cells in the traction battery and noticed a lot of corrosion on the bottom of the case (looks like maybe a leaking cell), but, did nothing about it. The battery is no longer giving me any problems, BUT...
    VERY intermittent P0AA6 code, red triangle, problem, etc. I hook Techstream up and read P0AA6, but do NOT see any information code.
    Again, it can be WEEKS between codes. Might be outside temperature related.
    I looked at the coolant reservoir and see SOME flow, I don't know how MUCH I should see.
    Here are my questions.
    How do I get the INF codes in Techstream? I do the HealthCheck, and all I get is the P0AA6, no inf code.
    Could this be a corrosion problem in the traction battery itself? I SHOULD have cleaned all the cells and the bottom of the case when I had it apart, but....
    Code is VERY intermittent, can be WEEKS apart. It ONLY happens when you are stopping.
    All help appreciated.
     
    #1 Bornloser, May 15, 2017
  2. andrewclaus

    andrewclaus Active Member

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    INF code should be in the freeze frame data. Click what looks like a snowflake.

    I certainly could be corrosion in the battery.
     
    #2 andrewclaus, May 15, 2017
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  3. Bornloser

    Bornloser Junior Member

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    Thanks, I will check next time it happens. I should have mentioned....It has been cool here and it hasn't thrown a code in weeks, but the last 2 days it has been in the 80's and has thrown the code 2 times in 2 days.
     
    #3 Bornloser, May 15, 2017
  4. Bornloser

    Bornloser Junior Member

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    Well, it has taken this long to throw another code. P0AA6 inf 526.
    A small bit of additional info. I have been watching the battery state of charge when I shut car of at night and again when I start it up in morning. Last night when I shut car off, the battery was fully charged (green). When I started the car this morning, the battery was only about 20%. So, is it safe for me to assume the problem is IN the battery? Since both the positive and negative are on relays that open when car is off, the ONLY path for discharge would be IN the battery itself, correct? This leads me back to the after effects of a leaky cell, so I have to tear the entire battery apart and scrub each cell and the case. Techstream reports all cells are good, within .1 volts of each other , and less than .2 ohm internal resistance.
    Am I correct in my thoughts? I think the fact the battery self discharged ONLY on the night before I got a code leads me to a battery problem, and cells look good except for residue of a leaky cell (that was replaced).
     
    #4 Bornloser, May 20, 2017
  5. andrewclaus

    andrewclaus Active Member

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    INF 526 is sort of a catchall, not much help. But again, corrosion in the battery case could be the problem and is probably the first thing to try to fix.

    It does not sound feasible that that much battery energy is being dissipated by a ground fault due to corrosion in the battery. The energy would have to go somewhere as heat. Even though block voltages and IR are good, there could be a capacity storage issue.
     
    #5 andrewclaus, May 20, 2017
  6. Beachbummm

    Beachbummm Senior Member

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    you are on the right track with leaking modules if you see corrosion in the case, unless you have a flood car. for some reason Toyota put the screw that mounts the module on the positive side, when it leaks it causes a short to ground..... it also makes the case charged so use thick rubber gloves when touching the case.. harbor freight sells them for 8 bucks. to see what ones are leaking use a multi meter to test them, negative to negative post, positive to the screw hole on the bottom on the positive side.. ANY voltage reading shows the mod is leaking.. just went through this on a 2008, found one leaker and a small rust spot..
     
    #6 Beachbummm, May 21, 2017
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  7. edthefox5

    edthefox5 Senior Member

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    P0AA6 is ground fault hi voltage leaking to ground. Severely corroded
    Battery assy.
    You can clear the ground fault by unbolting neg 12 volt.

    But continued driving with hi voltage leak has sometimes resulted in battery fire.
     
    #7 edthefox5, May 21, 2017
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  8. andrewclaus

    andrewclaus Active Member

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    And that must be the heat I mentioned in post #5. Definitely pay attention and be careful.
     
    #8 andrewclaus, May 21, 2017
  9. Bornloser

    Bornloser Junior Member

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    Thanks for all the info.
    I am currently looking at buying the battery cables (connecting the individual cells)and misc (some have the relays) from inside a used battery pack and just replacing them when I take the battery cells apart to clean them....just in case. I, of course, am looking at them on ebay...but think $100 seems a bit high for USED cables.
    Thanks for all the info, and will report back in a few weeks when project is done.
     
    #9 Bornloser, May 21, 2017
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