New Upper O-2 Sensor & Red Triangle of Death

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by The Bookfinder, Jul 10, 2026 at 1:33 AM.

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  1. The Bookfinder

    The Bookfinder New Member

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    my otherwise excellent mechanic shop just replaced the upper O2 sensor on my 2008 Prius. immediately after driving the 4 or 5 miles home, I started the car the next day and the red triangle of death is on! I'm afraid to drive it even back to the mechanic. I'm new to the Prius. And the engine light is back on which pulled the code for a minor vacuum leak. Changed out the gas cap, but haven't gotten any further. what about this death triangle. Plenty of new oil plenty of radiator water, flushed the brake system i'm not a very deep mechanic. I'can do a few little adjustments
     
    #1 The Bookfinder, Jul 10, 2026 at 1:33 AM
  2. Tombukt2

    Tombukt2 Senior Member

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    Why are you flushing brakes in a Prius if you're not much of a mechanic but anyway . Now need to read codes . With hopefully you're capable scanner
     
    #2 Tombukt2, Jul 10, 2026 at 4:39 PM
    Dennis Brown likes this.
  3. Dennis Brown

    Dennis Brown New Member

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    A lot of reasons. Could be as simple as an overheat temp of the hybrid battery (parked in the sun) or a more serious issue. If you have a code reader it can tell you the exact problem. They are rather inexpensive and will save a great deal of money, time and concern.
     
    #3 Dennis Brown, Jul 10, 2026 at 4:41 PM
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