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P0AA6 612

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Larry Newman, Sep 2, 2024.

  1. Larry Newman

    Larry Newman Junior Member

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    I have a 2008 Prius Touring that recently was the blessed recipient of a red triangle, VSC warning light, and brake warning light on the dashboard. Upon hooking into Techstream, further information revealed that the code was a P0AA6 isolation fault with subcode 612. I took the back of the car apart, battery out, etc. Upon inspection, I didn't see any obviously leaking modules or major issues. Everything looks to be in pristine condition except the bus bar bolts/connectors between battery cells. I looked around the forums and other websites for a couple hours to see if I could pinpoint a non-obvious 612, but I couldn't really find anything.

    I have attached pictures of the case, components, and battery cells. I have two leads after tinkering around with forum posts and a multimeter for 2-3 hours. I only attached one picture of the battery cells to avoid having to flip them over (my back is killing me after taking everything apart and sitting on a concrete floor). The bottoms of the battery cells are also in pristine condition; I checked all sides of every cell thoroughly twice to see if there was a leak without anything standing out.

    Lead #1 - If you see in the attached pictures of the case, there are some spots in the case. Compared to the other pictures of leaking batteries I've seen while researching, this doesn't look like cells leaking; it's also more evenly distributed throughout the entire length of the case so I would assume it's dirt or condensation spots or something else. Not really sure if this could still be cells leaking but if anyone has seen something like this, I would be very appreciative if you pointed it out.

    Lead #2 - I used a diagram file on another post I found while researching on where to use a multimeter to determine if there's a short on any of the connections. Everything was normal except for the resistance of the ground wire to some of the connections to the bus bar (the metal links meant to connect cells together). The diagram indicated that >10 ohms was the standard resistance, but I was seeing about half of that. The other connections were very close or over 10 ohms.

    Besides these two leads, I have precisely nothing that I can go off of other than replacing the battery cells and seeing if that fixes the issue. From what I've gathered from poking around, I'm open to replacing the battery cells (open to keeping the car as long as possible) and also cleaning the bus bar connections. My main desire for putting this out in the open is for some validation to ensure I'm not overlooking something obvious or something simple. I could always clean the bus bar connections or get a new cable then reassemble and see if it fixes it, but I'd like input on it first because I'm still a novice at the HV system.

    Any input is appreciated. Thanks.
     

    Attached Files:

    #1 Larry Newman, Sep 2, 2024
  2. Tombukt2

    Tombukt2 Senior Member

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    So you used your DVO hammer test meter to measure from ground to the bottom of every module that takes those little tiny screws since you've unracked this business I usually check this while it's all together put a test lead to ground and test one of the hybrid battery plug fuse sides. And see if the DVOM will count down to zero on the DC volt scale that should when you have this fault it will not and somewhere there's a leak and then while it's all racked up I leave the ground set up like it is and flip the battery up on it side and go down with the red lead and touch every one of those I don't know what is it 56 screws or something those little tiny bolts any of them that get a reading market with a black sharpie marker that's a problem. It looks like I see some spatter on your tray there those dark brown spots or whatever they got there somehow.
     
    #2 Tombukt2, Sep 2, 2024
  3. MAX2

    MAX2 Member

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    #3 MAX2, Sep 3, 2024
  4. dolj

    dolj Senior Member

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    You said modules correctly in the first instance, then pivoted to call the modules cells for the rest of the post. Modules contain 6 cells, so you can't really conflate the terms.

    That aside, it can be hard to spot the leaking electrolyte because it is almost invisible to the naked eye.

    With a P0AA6-612 the HV control ECU suspects the isolation fault to be located in the battery.

    Check the underside of each module where the screw insert is. This can be a failure point where a crack can occur and leak electrolyte out.
     
    #4 dolj, Sep 3, 2024
  5. MAX2

    MAX2 Member

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    An easier way to measure leakage is to measure the resistance between the bottom mount and either the (+) or (-) terminals of the module.
     
    #5 MAX2, Sep 3, 2024
  6. Tombukt2

    Tombukt2 Senior Member

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    Your battery computer the thing with the red label in the front of the case can also be a problem You need to break that flat plate off the back and look at the bars that go from the receptacle in the computer right to the green motherboard you'll see the mess clean that up My battery guy tells me those battery computers do go bad and he has replaced them a few times he seems to think that's more of a problem than battery modules I don't personally think so but whatever this is the thing that reads everything that flips the codes on for you so it could be problematic You may want to have a look at it
     
    #6 Tombukt2, Sep 3, 2024
  7. mr_guy_mann

    mr_guy_mann Senior Member

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    In pic # 6, the "big rusty" spot that extends around the module hold down bolt hole looks fairly suspicious to me.

    Large obvious stains aside, my procedure for testing a 612 INF isolation fault is to leave the pack assembled. Remove the service plug and the pack cover.

    Now I put one voltmeter lead somewhere on the pack high voltage circuit , the other lead on chassis ground. If I have ANY voltage (even millivolts), I unplug the battery ecu voltage sense harness and recheck. (It could also be a problem with any of the contactor relays or wiring, but very unlikely)

    Still have voltage to ground? Start removing a busbar "in the middle" of the battery section under test then check to either side of the removed busbar.

    For example, the service plug divided the pack from block 10 to 14 with the positive contactors "on one side"; and from 10 to 1 with the negative contactor "to the other side" . Keep "dividing and testing" until you have isolated the individual faulty module(s).

    Posted via the PriusChat mobile app.
     
    #7 mr_guy_mann, Sep 4, 2024
    Last edited: Sep 4, 2024
    Brian1954, Tombukt2 and MAX2 like this.
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