P0AA6 w 526 and 612 : I don't think it's the battery - what next?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Goneballistic, Aug 1, 2022.

  1. Goneballistic

    Goneballistic New Member

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    I have been lurking on PriusChat for a while, but running into an issue I need help with.

    Daughter's 2009 prius with about 180K on it threw the P0AA6 code last week. Assuming it was a leaky module, I:

    - pulled out the traction battery
    - took off the bus bars and checked each module.
    - charged the 12v battery to 100% just in case (it's about a year old, and was sitting at 12.6v when tested

    there is no current going to the case from any module. all modules look perfect. No modules are discolored, case is clean, dry and looks great.

    The bus bars were kinda corroded, so I took them out and threw them in a brass polisher and they look brand new now.

    Each cell tested almost exactly 7.5 volts. The largest variation was .2. I had a few 7.48, a couple 7.51, but largely they're all hovering right around 7.5v. I tested them all several hours later and voltage was the same.

    cleaned the little silver terminals that sit over the bus bars best I could and put it back in.

    It immediately threw the code again. I can only get it to drive by pulling out the connectors to the 12v battery and waiting a sec.

    Took it to a shop today, they charged me 150 bucks (OUCH) to pull the full codes and run a diagnostic. They got

    P0AA6 and codes 526 and 612. They also said the hybrid battery was at 0% and needed to be replaced. they quoted about 3500 to do that. Oddly, when I took the car in, it was almost fully charged on the onscreen display.

    I told them that I had checked the battery and it seemed fine, and the tech said maybe the ECU was bad.

    I drove the car home and the Hybrid battery was down to 2 bars, and they were purple. When I left it had almost full charge and was blue. That was weird. Almost like they discharged the battery checking it or something. I drove it home and the battery charged up, and right as I got home it threw the codes again.

    I'm going to pull the battery out again, what do I do next? Just replace the ECU and see if it fixes it? I'm going to look at the relays and cable, and order a megohmeter. I found this link in another thread and will follow this, but need to order a megohmeter first. I just have a normal one:

    145252_2006_Prius_RM_-_P0AA6.pdf

    should I just grab and ECU and go from there? What else is likely if it's not my battery? I'm going to do the voltage test right now where you test off the safety plug to the case and see what that says.


    She's got to head back to college in 2 weeks and with the price of gas, replacing a fuel efficient car is REALLY expensive right now, so I'm doing my best to help her out with it. I'll get pictures of the case when it comes back out.....
     
  2. Goneballistic

    Goneballistic New Member

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    tested lower bolt on the safety plug to the battery case and it's showing 49v pretty steady. according to the youtube video I saw, this means there is s leak in the battery, just not sure where. Could the ECU leak to the safety plug?

    When I checked the cell pins to the case, none of them showed any voltage. All were open circuits. So I don't think it's the cells themselves.
     
  3. bisco

    bisco cookie crumbler

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    if the hybrid battery were at 0%, the car wouldn't have started. kind of a scary shop
     
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  4. bisco

    bisco cookie crumbler

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  5. ChapmanF

    ChapmanF Senior Member

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    You've got the right ideas. The problem is somewhere within the 612 highlighted area. Just systematically test until you find it.

    [​IMG]
     
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  6. Goneballistic

    Goneballistic New Member

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    I may be missing something. Post 14 talks about new modules vs old modules. am I looking at the wrong post?
     
  7. Goneballistic

    Goneballistic New Member

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    I think I have to have a megohmmeter for this for sure. ordering one now
     
  8. PriusCamper

    PriusCamper Senior Member

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    Curious to know what kind of brass polisher you have? Is it basically like a rock tumbler, but the vibratory version? As for this voltage leak, I bet it's a bad module and you just have to find it. Wish there was a tool for that? Like one of those tools you can point at an electrical outlet and it tells you if its live or not by beeping. Seems if you had something similar but way more sensitive that could detect it? The milli-ohmeter might do that but I think the good ones cost more than $1K?
     
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  9. mr_guy_mann

    mr_guy_mann Senior Member

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    AFAIK, you don't use a megger to check the battery for an isolation fault (cables- yep, motors - yep). If your normal DVOM has a CAT III rating it should be fine. I would pull the service disconnect (HV fuse) and take the cover off the HV battery. The disconnect splits the battery in two.

    Carefully measure DC voltage from a module busbar on one side of the disconnect to chassis ground. (Should be 0 volts). Do the same for a busbar on the "other" side of the disconnect to ground.

    If either measurement show any voltage, unplug the orange voltage sense connector on the battery ecu and recheck. If the voltage is gone- the ecu (and likely connector) is the problem. It it's still there- remove a busbar in the middle of the section that has the reading and keep testing (then disconnecting) until you isolate it. Could also be in the cables to the contactors or the contactors.

    You can have a module fault where there is an internal crack and leak that allows voltage to "bleed" to the mounting screw on the bottom. Some faults are easily found by visual inspection- some aren't.

    Posted via the PriusChat mobile app.
     
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  10. ChapmanF

    ChapmanF Senior Member

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    Using a high-impedance voltmeter between terminals of the battery and body ground can be a way of detecting a leak. If the leak is from a battery module and if done early enough that there is likely to be only one leak, it can even give you a good idea of where in the stack of modules the leak might be. For example, the battery is about 201 volts 'wide', so if the voltage you measure from one end of it to body ground looks like, say, 90 volts, you might look for a leak around the 12th or 13th module from that end.

    The lower the impedance of the voltmeter, the less reliable that technique may be (it will bias the displayed voltage lower and make the leak appear 'closer' to the end you're measuring from), but you can mitigate that effect by repeating the measurement from the other end of the battery.

    If the battery has been throwing leakage codes long enough that by now it's likely to have more than one leakage path, then the technique isn't as useful. The meter will still show some voltage reading, but it will just be the Thévenin-equivalent voltage for the battery, the multiple leakage paths present, and the meter's impedance, and there won't be any easy interpretation of it as a physical location of a single leak.
     
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  11. bisco

    bisco cookie crumbler

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    sorry, post #24, click on the link at bottom for things to inspect for the 612 code.
     
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  12. Goneballistic

    Goneballistic New Member

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    I did this test detailed by this guy on YouTube


    This is the test from case to case, no resistance
    [​IMG]

    Test from front cable terminal to the battery case. No leakage
    [​IMG]

    Test to the rear post, no leakage from that part of the battery
    [​IMG]

    But then very oddly, I tested the lower, long cable from the end of that cable to the case and it showed low resistance and was bouncing around, so according to that test, there's a leak here somewhere

    [​IMG]


    Questions;
    1) is this a valid test?
    2) I'm thinking of isolating this cable and testing it's resistance or just replacing it.

    Good plan or bad idea?








     
    #12 Goneballistic, Aug 3, 2022
    Last edited: Aug 4, 2022
  13. Goneballistic

    Goneballistic New Member

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    it's not a vibratory polisher. it's a tumbler exactly like a rock polisher. In reloading often referred to as a "wet" tumbler because you throw your brass, the steel pins and fill it half full of water and lemishine polish. Sometimes a teeny bit of dishsoap.

    You use this tumbler and a bunch of little teeny stainless steel pins. they scrub everything off the brass and leave it looking brand new. In my case the bus bars look like brand new shiny copper.



    [​IMG]


    stainless steel pins.
    [​IMG]

    it's a great system, with the only drawback being the brass is polished in water, so you have to dry them out. You can air dry them, some pop them in the oven for a bit on low, and several people make brass dryers.

    for the bus bars I just put them on a towel and dried them all off thoroughly. I sprayed them down with WD-40 to displace any water, then wiped them as clean and dry as possible with blue paper towels. They look literally brand new.



     
  14. PriusCamper

    PriusCamper Senior Member

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    Thanks for clarification... I do same thing but without the pins... The edges of the copper bus bars seem more than adequate. But please post a pic of final result, perhaps your method is more shiny than my method?
     
  15. Goneballistic

    Goneballistic New Member

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    Just went and ran another test, this is them after maybe 20 minutes in the wet tumbler.

    You are right, you probably don't need the pins, the probably clean themselves. But the pins are a PITA to get out of the tumbler, and the advantage of the teeny pins is they actually go through the holes, so they get the inside of the holes as well as the surface. In brass they'll actually clean out the primer pockets. So they do a great job here.

    [​IMG]

    The rest of the bar. I could have gone longer and got every trace but this seemed good enough. If I get this working I'll order nickel plated ones
    [​IMG]
     
  16. Goneballistic

    Goneballistic New Member

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    I think I found it. I had originally watched this video, go to 3:42


    I had checked every cell resistance to ground. All of them showed infinite resistance, so no leak.

    So I assumed they were all fine.

    But based on what ChapmanF said, I decided to check with the Megger. The guy in the earlier video tested that way too.

    So I checked each side of the split battery. The long side of the pack, farthest from the ECU, showed voltage jumping around and low resistance

    [​IMG]


    So I pulled the bus bar and tested each cell. Cell 12-13 was low resistance and jumping around a bunch.

    Every other block showed infinite resistance/no current just like this
    [​IMG]


    I separated 12/13 and 13 shows low resistance. Every other cell showed infinite/4000Mohm resistance.

    So I think cell 13 is hosed. Ironically, my lucky number.

    [​IMG]


    Interestingly, my ohmmeter still shows no current from pin to battery case like I was expecting based on the YouTube video at the beginning of this post. This makes me nervous and I'm worried there's another issue somewhere since it shows no leakage to ground with the ohmmeter but shows leakage with the megohmmeter. Weird. But also, I'm dumb and there's probably something obvious I'm missing, like maybe 7.5v isn't enough to push electricity through the breach, but the higher voltage of the tester or battery under load is.

    In use, your can reset the codes by unplugging the 12v battery and drive the car and it will go from 10 seconds to several minutes before the code will set again, so that seems to line up with a small leak that only happens under some load, and not when the battery is at rest.

    I literally have no idea

    [​IMG]


    Also every cell including 13 show 7.76-7.78v.
    Which is good I guess.

    [​IMG]

    I have a quad port battery balancer on the way. I'll cycle the cells and balance them and reinstall a new one on 13.

    I still want to test this with ECU plugged into the voltage tracking wires, but I suspect the ECU is ok, and it's this cell.

    (Crossed fingers)

    I'm going to order 1 or 2 cells, plug them in and put it back in and see if we're fixed
     
    #16 Goneballistic, Aug 4, 2022
    Last edited: Aug 4, 2022
  17. PriusCamper

    PriusCamper Senior Member

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    Congrats... Always very impressive and enjoyable when someone with the smarts and skills works thru these challenges so well so we can sit back and enjoy you figuring it out rather than helping too much.

    And if you're looking for a good replacement module, professor Joe in Oregon teaches this stuff at his local college and has replaced his more than $20K lab-grade testing gear twice with a similar priced brand new station in past 5 years since I've known him.

    As in 3 times he's spent more than $20K on battery testing gear. An amazing resource and always willing to chat via text or phone call His spare modules last I checked are $35 and always the strongest modules in a pack I rebuild. https://2ndlifebattery.com/
     
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  18. Goneballistic

    Goneballistic New Member

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    I'll order some right now, the one I was looking at on Amazon is showing a delivery date of aug8th to 25th lol. That's not gonna work.

    I'll get one from him now
     
  19. PriusCamper

    PriusCamper Senior Member

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    I'll text him and see what he says for delivery time... I was about to text him about some others stuff.
     
    #19 PriusCamper, Aug 4, 2022
    Last edited: Aug 4, 2022
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  20. TMR-JWAP

    TMR-JWAP Senior Member

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    The harness that has the voltage sensing tabs is called "wire frame #2" and plugs into the ECU. While you have it apart, it would be prudent to inspect the ECU socket and the harness plug. They are very frequently victims of corrosion and will cause problems. Typically, it will be 3 or 4 pins turning black. Advanced stages will have significant green buildup at the pins. More advanced will have pins breaking off. The entire wire harness (assembled with bus bars) is available from Toyota for about $60.

    If you do reuse the one you have, keep in mind DIYers often run into problems with the sensing tabs breaking or cracking at the crimp area. Even a partial crack will cause sensing variations that will cause the battery to code.
     
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