1. Attachments are working again! Check out this thread for more details and to report any other bugs.

Gen 2 05 P0AA6

Discussion in 'Gen 2 Prius Technical Discussion' started by Buffalo Bill’s Prius, Feb 16, 2023.

  1. Buffalo Bill’s Prius

    Joined:
    Feb 8, 2023
    9
    0
    0
    Location:
    Orange County
    Vehicle:
    2005 Prius
    Model:
    Base
    Hello!

    I’ve got a P0AA6 red triangle on a 167k Prius.
    Using a test recommended in different threads I identified that the high voltage leak is in the HV battery. (Triangle appears within 60 sec of being in not ready mode).
    The test ruled out the transmission or inverter (imho)

    The Dr Prius app tests did not show any problem with the battery modules, at least not to my eyes. I ran several tests (picture included) 4/5 tests showed no issues.

    The dealer recommend that I clean the corrosion off of the battery. I have purchased gloves and tools to do this.

    Will anyone be kind enough to help me decipher the DR Prius results and advise if I should attempt to clean corrosion or purchase a a new HV battery?
     

    Attached Files:

  2. TMR-JWAP

    TMR-JWAP Senior Member

    Joined:
    Aug 12, 2016
    6,182
    5,869
    0
    Location:
    Columbia, SC
    Vehicle:
    2007 Prius
    Model:
    Touring
    The P0AA6 HV Isolation fault has nothing to do with individual module voltages, and it's exact location in the battery cannot be determined using them. Most of these instances are caused by electrolyte seepage from the module making contact with the metal battery case. Corrosion only on the busbars will not cause a P0AA6.
    I've seen seepage from 3 common locations on a module:
    1. from one of the module terminals. You'll see blueish residue on the module case below the terminal. (could be dry or wet)
    2. sometimes it is due to a small crack on the bottom of the module
    3. there is a steel insert pressed into the bottom of the module for the mounting screw. Sometimes an internal crack in the housing will allow electrolyte to make contact with this steel insert, which in turn, is contacting the metal case.
    4. very often, you can see a brownish stain on the metal case at the bottom of the modules where seepage has corroded the metal. I had one battery that actually had a drip on the bottom from a crack.
    Other than the P0AA6, your battery looks to be in pretty good condition. You can disassemble and clean the modules to remove the seepage residue. Then take a voltage reading between the metal insert on the bottom of each module and each of its terminals to see if there is a steady DC voltage reading. There will often be a small reading that quickly dissipates to near zero. Any module with a steady voltage reading during this test should be replaced. I've even experimented with modules that have this problem and was able to eliminate the P0AA6 by cutting 2 pieces of 3M electrical tape to match the width of the module and placing them over the metal insert. Reassembled the battery but did not use a mounting screw on that one module. The "grounded" module was effectively isolated from the metal case. That experiment is still ongoing, as the battery is still in service in one of my Gen 2s.

    Prior to disassembly, you can make an overall check by removing the safety disconnect (in case you haven't already done that, safety first) and connecting one meter lead to the metal case and then touching the other lead to each main relay (on the battery side under the white plastic covers). On a good battery, these reading should be effectively 0 volts. If one or more of the modules is "grounded", you'll see a steady voltage reading. Typically in the double digits.

    Can you post photos of each side of the modules so we can see the entire case surface?
     
    #2 TMR-JWAP, Feb 16, 2023
    Last edited: Feb 16, 2023
  3. Tombukt2

    Tombukt2 Senior Member

    Joined:
    Nov 29, 2020
    8,803
    1,536
    0
    Location:
    Durham NC
    Vehicle:
    2009 Prius
    Model:
    Base
    So this is an original battery on this 05 generation 2.. personally I would say it's getting into the range of time and mileage to be doing something about the battery You want to do the repair whack-a-mole thing. Then that's what you'll continue with. I chose not to do that and bought a battery apparently at a good time to do that I spent about $1,400 cash and carry from a Toyota dealer brand new not rebuilt I needed the car more than I needed to play or work or whatever we're going to call it I don't play whack-a-mole at the fair I'm not going to play it in my vehicle I might play it on my lawn mower or something but not in something that I need pretty much daily or I don't eat.
     
  4. TMR-JWAP

    TMR-JWAP Senior Member

    Joined:
    Aug 12, 2016
    6,182
    5,869
    0
    Location:
    Columbia, SC
    Vehicle:
    2007 Prius
    Model:
    Touring
    Tom, you jerry rig every thing else on your cars and do so many jobs half by procedure and half by how you feel that day. Why so "OEM" on an HV battery? I figured you'd have just dropped in some 6v lantern batteries and called it a day.....

    A P0AA6 is completely different from a P0A80.
     
  5. Buffalo Bill’s Prius

    Joined:
    Feb 8, 2023
    9
    0
    0
    Location:
    Orange County
    Vehicle:
    2005 Prius
    Model:
    Base

    Thank you so much for this write up. I have ready many and this was so detailed that it really motivated me to continue this procedure.
    The original pictures were taken by the dealership during inspection and I had not removed the battery myself at the time of the original post.
    I have just removed the battery myself and have begun to inspect.
    Thank you for clearly stating that the corrosion on the bus bars won’t throw the code.
    The battery has a ton of debris on the modules (dust balls, hair!, gunk) but no obvious leak of electrolyte.
    There is a very suspect water marking next directly underneath the hose insert.
    Tomorrow I will finish removing the bus bars and will conduct the readings attaching the lead to the case and the terminals.
    Thank you again
     
  6. Buffalo Bill’s Prius

    Joined:
    Feb 8, 2023
    9
    0
    0
    Location:
    Orange County
    Vehicle:
    2005 Prius
    Model:
    Base
    Here are some pictures of the battery
     

    Attached Files:

  7. Buffalo Bill’s Prius

    Joined:
    Feb 8, 2023
    9
    0
    0
    Location:
    Orange County
    Vehicle:
    2005 Prius
    Model:
    Base
    Thank you,

    I am also very reticent about playing the mole game. I understand your reservations about “playing” with my primary means of transportation. I don’t plan on keeping this car very much longer as it can’t pass smog due to fake cats (stolen) and o2 sensor bypass. I might buy a refurbished hv for 700
     

    Attached Files:

  8. mr_guy_mann

    mr_guy_mann Senior Member

    Joined:
    Sep 3, 2020
    3,406
    1,473
    0
    Location:
    NJ-USA
    Vehicle:
    2006 Prius
    Model:
    Four
    Whatever route you go, be sure to tighten the bus bar nuts to 48 INCH-pounds with a torque wrench.

    Posted via the PriusChat mobile app.
     
  9. Tombukt2

    Tombukt2 Senior Member

    Joined:
    Nov 29, 2020
    8,803
    1,536
    0
    Location:
    Durham NC
    Vehicle:
    2009 Prius
    Model:
    Base
    Yes if you're dumping the car dudu management problems that are beyond your control like check engine lights and cats and you live in places where that can't be rectified with paperwork then of course you have no choice so then no matter oh well made up battery can go 3 to 4 years you'll be out of the car by then for sure
     
  10. Buffalo Bill’s Prius

    Joined:
    Feb 8, 2023
    9
    0
    0
    Location:
    Orange County
    Vehicle:
    2005 Prius
    Model:
    Base
    Gentleman
    A reading of each module with the volt meter connected from the base to each terminal revealed that module 23 was grounded.
    Upon removal we found a very badly corroded connection around the base of the module where the mount is.
    We removed the corroded material.
    Could this be the culprit of the code?
     

    Attached Files:

    #10 Buffalo Bill’s Prius, Feb 18, 2023
    Last edited: Feb 19, 2023
  11. ChapmanF

    ChapmanF Senior Member

    Joined:
    Mar 30, 2008
    23,660
    15,352
    0
    Location:
    Indiana, USA
    Vehicle:
    2010 Prius
    Model:
    IV
    It appears that your meter thought so. Its opinion is worth more than mine.
     
  12. Buffalo Bill’s Prius

    Joined:
    Feb 8, 2023
    9
    0
    0
    Location:
    Orange County
    Vehicle:
    2005 Prius
    Model:
    Base

    Quick summary,
    We cleaned corrosion off of module 23 and put the battery back in the car. We did not replace the module and it remained grounded to the battery case.

    Upon reassembly I got two new codes P0A0D and P3000 (no more P0aa6)
    Reconnecting the Orange plug correctly cleared the first code.
    The car will drive but the P3000 code remains and immediately comes on upon ignition.
    I have given up on this repair and I plan to buy a refurb on Monday. I don’t have the will to replace the grounded module and then load test each of them. I say this with great disappointment in myself since it feels disrespectful to this great community not to follow through

    I want to add, with embarrassment, that we accidentally broke a wire underneath the cells. It is a wire that connects to 3 modules underneath them with plastic black clips. They are two wires that feed from the ecu to the last cell. (I lack dexterity)

    I want to thank you all sincerely for the guidance you’ve provided this far and for every reply.
     
    #12 Buffalo Bill’s Prius, Feb 19, 2023
    Last edited: Feb 19, 2023
  13. TMR-JWAP

    TMR-JWAP Senior Member

    Joined:
    Aug 12, 2016
    6,182
    5,869
    0
    Location:
    Columbia, SC
    Vehicle:
    2007 Prius
    Model:
    Touring
    You could eliminate the "grounded to the case" by placing a small square piece of electrical tape on the bottom of the module to cover the metal insert. Do not install the mounting screw for that module. The tape will provide insulation between the insert and the case, effectively removing the "ground" condition, just like if you were to use electrical tape to wrap an exposed bare wire.

    The wires on the bottom of the battery are for the three temperature sensors (thermistors). typically, these break right at the thermistor if stretched very tight and are not repairable. Happens quite often when the battery is being disassembled and it's forgotten that these are attached to the modules. If one of them is broken off, perhaps that is the source of the P3000? I seem to remember those sensors each having their own code or subcode, but I'd have to look that up again to verify. Another member located a suitable replacement thermistor on Amazon for a few dollars that could be spliced into the wires. The entire OEM wire harness can also be purchased on ebay.
     
    #13 TMR-JWAP, Feb 19, 2023
    Last edited: Feb 19, 2023
    SFO likes this.