Help! Is the battery dead or something else?

This doesn't sound like dead battery to me. Counterintuitive, but maybe try starting it one more time? There's a cold-start phenomena: the engine knocks badly at start up, and sometimes is ok if shut down and restarted. There might be a cause-and-effect, that the car was started cold and then quickly shut down, say the day before.

It's by no means acceptable or normal, and it's something Toyota is aware of, looking in to.

Anyway, just for giggles: try one more start up?

 

You can get a multimeter and check the 12v battery voltage. I'm thinking if it'll get into Ready mode, it probably isn't a battery problem. But best to check it, it's should be replaced after 5 years anyways

 

if it's not the 12v, i would have the codes read. could the high pitch noise be an alarm?

 

I would say it's a bad 12v

 

Agree bad battery

 

+3 on the bad battery.

And some of these models are known to make a horrible knocking noise if left unused for several days in a row; totally different problem......which Toyota claims is not really a problem.

If this happened after the car sat unused for several days, all the pieces seem to fit.

IF it has the original 12 V battery, you should have it changed.......even if the shop claims it is not the problem but they can't find out what IS.

 

Not convinced.
Bad plugs WILL NOT prevent the car from going into READY mode and trying to start.

 

be careful, it could be one of those deals where they just keep trying things, and you just keep paying them.
are you at a dealer, or respected hybrid shoppe?

 

when you talk about high pitch whining, ready mode, banging noise, accelerating instead of braking, it just doesn't add up. replacing the plugs 20,000 miles early is not a big deal, i'm just saying i hope they're not just using a process of elimination method.

have they tested the 12v?

 

If you have a chance, please post any and all diagnostic codes that were retrieved by the shop. That should really be step one of any diagnosis.

The idea of blaming the 12 volt battery first, based on sort of vague reasoning that 'computers do weird things on abnormal supply voltage, so no matter what codes I have, they could be caused by that, instead of meaning what the codes mean' tempts a lot of people—maybe because it sounds like less trouble than having the codes read, and it seems to offer the chance of an easy fix and nothing really being wrong with the car, and wishful thinking is powerful. On the other hand, in case there is a real problem and the codes mean exactly what they mean, wishing it's the battery just slows down finding and fixing the problem.

In my own experience (I've only owned two Prii, a Gen 1 and a Gen 3), I've had various mishaps drain the battery south of 8 volts more than once, which makes it pretty hard to start the car, but hasn't ever caused either of my Prii to log codes that didn't mean what the codes meant.

The high-pitched noise puts me in mind of the braking system alarm, which is only used for certain brake system codes, not for minor, non-urgent ones. So I'd be extra attentive to retrieving any possible brake system codes.

-Chap

 

I recently had to replace my 12v battery (bought yellow top Optima). In my case the dash lights stayed on but the READY light never appeared. I tested the old battery when I took it out, 9.9 volts.

 

You are somewhat lucky.
MANY other owners over MANY years have had that happen.
When multiple codes show up all of a sudden, that point to various DIFFERENT sub-systems........or the car won't go into READY mode.....a good place to start BASED ON THE EXPERIENCE OF OTHERS is to test the 12 V battery and it's connections.
If you don't do that, it can end up being an expensive mistake. That too has been reported by more than a few owners.