Horn honking and won’t go into drive

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Andrew Colvin, Oct 2, 2018.

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  1. Andrew Colvin

    Andrew Colvin Junior Member

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    I recently purchased a used 2010 Prius. The dealer put in a new hybrid battery and all seemed well. I have had it for about a month and just yesterday, I left my house and all of a sudden the horn started honking non-stop while driving. I pulled over and turned the car off but it continued to honk. I turned the car on an off a few times and it stopped.

    After this, I attempted to drive and it started again. I jumped out and pulled the 12v battery to make it shut up so I could try to figure out what was going on. Looked up fuse info and went to pull the horn fuses so I could drive it back—but there were none. Both the fuse slot and fuse relay spot listed as S-Horn were empty. (I later found out the horn was not part of that and under a different fuse.

    Nevertheless, when putting the 12v battery back, the horn would start again. I drove it home honking. When I got home, I found that I could no longer put the car in drive. All the dash lights are on. Except for the orange triangle. It flashes briefly when I move the shifter into drive.

    I’m at a loss. I ordered a new 12v optima battery for the hell of it. But it seems like something major is wrong. I tried pulling the fuse that controls the lights and horn, but it is part of a three fuse section that controls the anti-lock brake system. That stopped the horns but the car was still undrivable. I put it back and manually and temporarily unplugged the two horns instead.

    Any ideas?
     
    #1 Andrew Colvin, Oct 2, 2018
  2. PriusCamper

    PriusCamper Senior Member

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    Return you Optima battery right away... They're total garbage... If you read BBB and other Consumer reviews about Optima you'll realize they are a bunch of crooks and shouldn't be allowed to sell their garbage to anyone.

    Even an Optima dude on here back in the day before they decided they'd be better off not being publicly available said when people return defective batteries they just recharge them and sell 'em again because his customers are stupid. Doesn't even test the battery...

    As for your horn problem... There's a short circuit in that part of your car's wiring and it's getting worse to the point that you car won't start, either because an additional fuse blowing, or the car computers sensing a ground fault and shutting it down. Study the horn switch, inspect the wires that go from the horn into the wiring harness for damage. Maybe test the horn separately from the car to make sure it's functioning normally.
     
    #2 PriusCamper, Oct 3, 2018
  3. Andrew Colvin

    Andrew Colvin Junior Member

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    Thanks for your suggestions! From my experience, and from many others, the optima battery appears to be the best option you can buy.

    Nevertheless, my current 12v is fine and I’ll be returning the new one. I took the Prius to my mechanic and he has been running lots of tests and trying to pin down the problem. Of course, there are no dash lights on for him and everything works fine. Typical!

    It is looking like one of the primary relays has gone bad. It’s had heat and has warped so the plates aren’t making a clean contact. I’ll find out today if that is the root cause.
     
    #3 Andrew Colvin, Oct 5, 2018
  4. Andrew Colvin

    Andrew Colvin Junior Member

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    So it turns out it was a combination of the aftermarket security system and the bad relay. Both have been fixed and the problems are solved. Except for the head unit problem. The test device can’t communicate with the nav system or park assist. I’ve been advised that I will likely need to replace it.
     
    #4 Andrew Colvin, Oct 5, 2018
  5. PriusCamper

    PriusCamper Senior Member

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    Optima battery is best option? You don't even state why? Let's talk amp hours... The very best for Prius is wheelchair batteries up at 55 amp hours, or at least the ones they sell at auto parts stores as #1 replacement for Prius 12v in the 45 amp hour range, yet you want to argue that a garbage battery at less then 30 amp hours is the "best option you can buy." Go ahead, we're all ready for you to prove your point... Go ahead and prove that an Optima 12v is even capable of producing the amp hours that they claim? Show some data and proof please!
     
    #5 PriusCamper, Oct 6, 2018
  6. Grit

    Grit Senior Member

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    I want to see the battery unwarped the relay, it’s that good of a product to randomly buy.
     
    #6 Grit, Oct 6, 2018
  7. PriusCamper

    PriusCamper Senior Member

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    What does that even mean? "Unwarped the relay"

    Are you trying to say that really crappy batteries are safer because they have no power and won't damage the vehicle even though you're rolling around with enough amps to melt forged steal at 1500 degrees?
     
    #7 PriusCamper, Oct 6, 2018
  8. ChapmanF

    ChapmanF Senior Member

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    I don't know, but I read it as a comment on the PriusChat tradition of pushing battery replacement on new posters in advance of helping them find out what's wrong with the car.

    Per the OP in #4, what was wrong with the car was a bad relay and an aftermarket security system (plus a couple of communication issues yet to be diagnosed).

    -Chap
     
    #8 ChapmanF, Oct 6, 2018
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  9. Usle

    Usle Active Member

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    Reading the thread my first thought was aftermarket alarm, and Shazam, it was the aftermarket alarm.
    Any sign of rodents in the interior or cabin filter, hope not.
    And yes, wierd electric problems are often a weak 12v battery, and yes the optima is a good choice, much better than the OEM.
    Wow, a new traction battery, well worth the effort to get everything fixed and then enjoy another 150,000 care free miles.
     
    #9 Usle, Oct 6, 2018
  10. Andrew Colvin

    Andrew Colvin Junior Member

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    Unfortunately, despite a new traction battery, fixing the electrical issue, and replacing the entire head unit, I still get the "check hybrid system" indicator. What could possibly be wrong!? I am beginning to hate Prius. :(
     
    #10 Andrew Colvin, Oct 6, 2018
  11. PriusCamper

    PriusCamper Senior Member

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    Have the symptoms change though? For example are you able to get it into drive?

    And what are the subcodes for the Hybrid battery system?

    Sometimes with brand new battery packs you can get some anomalous codes in the first 70 miles. But you want to be very careful to make sure battery doesn't heat up and no new codes arrive when your putting in those miles / checking to see if that's the case.

    When you say replace "head unit" are your referring to Hybrid Battery ECU, sensors, etc. or something else?
     
    #11 PriusCamper, Oct 6, 2018
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