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

    Joined:
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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

    Joined:
    Mar 30, 2008
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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
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