'08 Prius P0AA6 hybrid battery isolation fault in battery and ecm

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Patio, Jul 24, 2023.

Page 2 of 2
  1. Patio

    Patio Junior Member

    Joined:
    Jul 24, 2023
    21
    8
    1
    Location:
    Tallahassee, FL
    Vehicle:
    2008 Prius
    Model:
    SE
    Thank you, thank you! I noticed after the Prius was sitting in the driveway for a week without any panels in the trunk area that there was liquid in the left side well (opposite the battery). My front windows are also not going up and down as smoothly as I'd like them too It's time to tackle these other problems now.
     
    #21 Patio, Aug 28, 2023
    bisco likes this.
  2. dolj

    dolj Senior Member

    Joined:
    May 14, 2012
    8,324
    4,251
    0
    Location:
    Wellington, New Zealand
    Vehicle:
    2007 Prius
    Model:
    N/A
    Well done!
    No doubt.
    I don't want to rain on your parade, but what you're saying is much like, "I installed new lithium batteries in my flashlight and it is so much brighter!" It's not really the lithium, it is the fact they are new batteries.

    Anyway, having a new battery will be like chalk and cheese coming from the worn-out battery. Continue enjoying the new car feel.
     
    #22 dolj, Aug 29, 2023
  3. Mongolian prius

    Mongolian prius New Member

    Joined:
    May 23, 2025
    6
    0
    0
    Location:
    Mongolian
    Vehicle:
    2012 Prius
    Model:
    III
    Hello. I can't find the voltage drop on my gen 2. I replaced the battery on another car and the same error occurred after 20 seconds. Should I try changing the inverter next time? How can I make a correct diagnosis?
     
    #23 Mongolian prius, Sep 23, 2025 at 8:08 AM
    Last edited by a moderator: Sep 23, 2025 at 5:02 PM
  4. Tombukt2

    Tombukt2 Senior Member

    Joined:
    Nov 29, 2020
    12,675
    2,263
    0
    Location:
    Durham NC
    Vehicle:
    2009 Prius
    Model:
    Base
    Codes and sub codes are important.
     
    #24 Tombukt2, Sep 23, 2025 at 9:02 AM
    Brian1954 likes this.
  5. Tombukt2

    Tombukt2 Senior Member

    Joined:
    Nov 29, 2020
    12,675
    2,263
    0
    Location:
    Durham NC
    Vehicle:
    2009 Prius
    Model:
    Base
    Which battery are you dealing with the big one or the little 12 volt?
     
    #25 Tombukt2, Sep 23, 2025 at 10:05 AM
  6. ChapmanF

    ChapmanF Senior Member

    Joined:
    Mar 30, 2008
    27,035
    17,733
    0
    Location:
    Indiana, USA
    Vehicle:
    2010 Prius
    Model:
    IV
    If I may ask, what 'error' do you mean, and how have you determined the 'same' error recurred?

    If you have used a scan tool to see the error code, please include that code.

    This existing thread is about the error code P0AA6. If you have some different code, it will be better to start a new thread.

    If P0AA6 is the code you have, then a 'voltage drop' is not what you are looking for. You are looking for an isolation failure somewhere in the high-voltage system, such that there is a slightly-conductive path somewhere between the high-voltage system and the car's low-voltage system or the body metal.

    With a P0AA6 code there will also be a three-digit subcode that can save 75% of your diagnostic effort by narrowing the search for the problem into one of four smaller areas:

    [​IMG]

    If you do not have a scan tool able to show you the three-digit subcodes, you can simply work through all the troubleshooting steps for all four areas until you find the problem. You can also search for threads in the 1st-generation Prius forum here that describe techniques for narrowing down the fault area that worked in gen 1 (which didn't have the helpful three-digit codes). (When searching the gen 1 forum, look for the equivalent gen 1 code P3009, instead of the later, standard, P0AA6.)
     
    #26 ChapmanF, Sep 23, 2025 at 11:28 AM
(You must log in or sign up to post here.)
Page 2 of 2