Horn honking and won’t go into drive

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.

 

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!

 

I want to see the battery unwarped the relay, it’s that good of a product to randomly buy.

 

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?

 

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

 

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.

 

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?