New to me owner with red triangle

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by sandmanx, Jun 22, 2026 at 11:05 PM.

  1. sandmanx

    sandmanx New Member

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    Location:
    Texas
    Vehicle:
    2009 Prius
    Model:
    II
    Hello everyone. I picked up a 2009 Prius a month ago with 272K miles on it, and now I have close to 275K miles. When I was driving the car on Saturday back from my nearest town(I'm in rural Texas), it all of a sudden threw up a red triangle about 4 miles from home, and I limped it home and parked it. It won't start up now, and using the OBD Fusion app on my phone I am reading these codes: P0137(an oxygen sensor, it threw this on Thursday last week and I haven't gotten a replacement ordered yet), P1121(it's been on and been low priority) and P0AA6. It seems that my app can't read the sub code on that last error and I think that's what's causing the issue. What would be the best move from here to get it back up and running? I typically do my own mechanical work and I'm experienced with DIY off grid solar for my house setup for what's that worth.

    Thanks
     
    #1 sandmanx, Jun 22, 2026 at 11:05 PM
  2. ChapmanF

    ChapmanF Senior Member

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    Location:
    Indiana, USA
    Vehicle:
    2010 Prius
    Model:
    IV
    The P0AA6 is why the triangle is on, yes.

    The INF code just saves time in your diagnosis by placing the fault in one of these four areas, so you don't waste time looking for it in the other three.

    [​IMG]

    If you aren't at all able to get your hands on a scan tool that shows you the INF code, you can still find the fault, it's just more work.

    You can look for threads on how gen 1 owners had to proceed (they didn't have the handy INF codes yet, and the code was P3009 in that generation, because SAE hadn't standardized P0AA6 yet). You'll have to adapt what you find there a little, because gen 1 didn't have electric air conditioning (the INF code 611 area).

    Oo, I didn't realize 'til now there's also a Carolyn Coquillette video about that. You're in good hands now.

     
    #2 ChapmanF, Jun 23, 2026 at 8:06 AM
    Last edited: Jun 23, 2026 at 8:18 AM
  3. JC91006

    JC91006 Senior Member

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    Location:
    Los Angeles, CA
    Vehicle:
    2008 Prius
    Model:
    II
    At 272k miles when you bought it, these cars usually will have problems. If you were able to drive 3k since, I am guessing your most likely cause to be a bad Hybrid Battery causing that error. A leaking module inside the battery. But that's just a guess, at your mileage it could be anything that's causing that (transaxle, AC, battery, inverter)

    When you get this error, you can start the car once before it disables itself again. To start it, you would have to disconnect the 12v battery and erase the code. Once erased, the car will start 1 time. If you need to move the car, that's the method you would use.
     
    #3 JC91006, Jun 23, 2026 at 10:18 AM
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