Incessant honking + red triangle of death

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Alex H, Sep 8, 2025 at 6:34 PM.

  1. Alex H

    Alex H New Member

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    My 2008 Prius is honking incessantly. It's a really weak, pathetic, but very-much-there, constant horn blowing. I live in NYC with street parking, so I was parked a block from home and just happened to walk past it (definitely made friends with the neighbors over this), so I have no idea how it was going on. I was able to turn on the car (still had enough juice to start), but found a red triangle of death when I turned it on. It continued honking, even with the car turned on, so I unplugged the battery. Based on some other recommendations here, I changed the 12v battery, but unfortunately the honking continues, and now the car won't start. Has anyone experienced anything like this, and any suggestions before I tow it in to a shop?

    It only has about 120,000 miles, and I'm the only owner, but outside life has been rough for this one.
     
    #1 Alex H, Sep 8, 2025 at 6:34 PM
  2. PriusCamper

    PriusCamper Senior Member

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    I suspect blasting your steering wheel with compressed air would be a good first step to deal with the horn. Then inspect the physical horn and wiring... As for red triangle, there's a chance that low 12volt from honking so much would cause that. But likely something different and not related.

    If you get one of these devices you can read and clear the error code that likely got stored when that red triangle showed up by using a phone app like Dr. Prius: http://www.ebay.com/itm/265484403768
     
    #2 PriusCamper, Sep 9, 2025 at 8:15 PM
  3. Tombukt2

    Tombukt2 Senior Member

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    How about to start just unplugging the horn? Then you can use a test light in a fixture to test that horn still active . Then play with horn button pad . Is the alarm or Immo active ?
     
    #3 Tombukt2, Sep 9, 2025 at 8:54 PM
  4. PriusCamper

    PriusCamper Senior Member

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    If only I knew what a "horn button pad" was and I'd make it my first tattoo.
     
    #4 PriusCamper, Sep 10, 2025 at 12:10 AM
  5. Tombukt2

    Tombukt2 Senior Member

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    Horn pad is the thing with airbag in it wen you depress that lil metal bars move I'm sure they're are videos showing steering wheel apart . The springs the black wire etc
     
    #5 Tombukt2, Sep 10, 2025 at 9:03 AM
  6. Tombukt2

    Tombukt2 Senior Member

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    If it's unplugged it can't drain the battery I realize horn won't work .
     
    #6 Tombukt2, Sep 10, 2025 at 9:04 AM
  7. Alex H

    Alex H New Member

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    Thanks for the recommendation on the OBD2 scanner, PriusCamper. My last one stopped being supported, and I never replaced it.

    Turns out the issue was the whole fuse box deteriorated from all the weather, salt, and 13 years of outdoor parking. That was the cause of the intermittent starting and shorting the horn. My mechanic happened to have a fuse box from a scrapped 2nd gen Prius on hand, but it didn't have enough circuits to fit my 2008 Touring model. He advised we could search eBay for a used one, with potentially variable success. New OEM is $1200 before labor, but considering my milage is so low, I'm going to replace it. Fingers crossed!
     
    #7 Alex H, Sep 10, 2025 at 1:10 PM
  8. pasadena_commut

    pasadena_commut Senior Member

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    Uh, if the fuse box rotted out, how is the rest of the car doing? Naively I would have thought the fuse box would go long after the frame did.
     
    #8 pasadena_commut, Sep 10, 2025 at 8:02 PM
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  9. gdanner

    gdanner Member

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    I experienced a similar situation when the 12V battery in my 2005 Prius ran down to ***nothing*** after I didn't drive the car for several weeks. I suspected my 12V battery was getting old and weak. Still, I was surprised when it went totally dead. But that 12V battery was more than 5 years old. I'm not surprised it needed replacement.

    Anyway, at first I tried to recharge the dead 12V battery by connecting a small (4 amp) battery charger to the 12V "jump start" terminals inside the engine compartment fuse box. Doing this set off the repetitive horn beeping and lights blinking scenario.

    Next I tried connecting real jumper cables from another car. That worked fine.

    Later I found that I could use my small battery charger as long as the 12V battery was still somewhat charged to begin with. Evidently my little charger wasn't able to supply enough 12V power to initially "wake up" the Prius.
     
    #9 gdanner, Sep 12, 2025 at 2:01 PM
  10. ChapmanF

    ChapmanF Senior Member

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    I shudder to think of the labor. The fuse box is built in more than one module, and some are easily replaceable, while others are basically integral with the wire harness. Sounds like a very tedious repinning job.
     
    #10 ChapmanF, Sep 12, 2025 at 6:30 PM
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