Battery Problem?

Does 'READY' come on?

 

Get the smaller battery, next to the traction battery checked out first. If that's low, it'll throw a lot of senseless codes.
If you can buy a friend lunch to remove the battery and take it to any automotive parts store for a free test. I believe that one is in the back passenger side trunk area or under the rear seat.

Hope this helps...

 

rear right corner under the hatch floor. get a free load test at many auto parts stores.

 

This is not about your hybrid battery.

The 12vdc battery powers all computers. When it dies you can not go into READY.

 

Don't waste your time at autozone, they don't know anything about hybrid batteries,
or testing a Prius 12v battery.
How old is the 12v battery? Do you have a battery charger? If it's 5 amps or less,
charge the 12v battery for 4-8 hours. Then remove the charger and wait an hour,
check the voltage. It should be at least 12.5 volts, if i'ts lower, it's time to replace it.
Then charge it for 8 hours to give it a full charge, before installing it.

It the 12v battery is weak, computers cannot start properly and the hybrid system
will not activate correctly giving you errors.

 

If you have warning lights on the dash, you need to have the trouble codes read with an OBD2 scan tool. You can purchase one yourself or have someone else do it like an auto parts store or mechanic or a friend.
If you want to purchase a scan tool, take a look at this thread:https://priuschat.com/index.php?posts/3290690

 

For some (but not all) of the warning lights on the dash, you can also get the trouble codes without a scan tool, this way:

Blink (a/k/a Flash) Codes – How to. | PriusChat

 

Well, you need to get a code reader, and find out what the codes are. That will point you in the
right direction on what the problem is. The "check hybrid" display can come up for several reasons
that are not releated to the actual hybrid battery. That is the 200+volt battery that helps drive the car.
The 12volt is the low voltage battery that powers up the computers and if all is correct, will allow the
hybrid system to start.
The 12volt battery works pretty much the same way is a non hybrid car. But it does NOT turn the motor
over to start the car, the hybrid battery does that.
If the 12v battery is weak, all kinds of hybrid issue will arise, that likely aren't an issue, once you have a healthy
12v battery.
That's why everyone asks how old the 12v battery is. So, how old is it? Since you purchased the car in 2019,
5 years ago, the 12v battery is likely getting old and weak. MAYBE, a 5amp or less AGM charger can be used
to charge the battery for several hours and may be healthy enough get your car going.
It's likely older. If you remove the covers in the trunk, and the cover over the 12v battery on the passenger rear side,
you can hopefully see a date sticker on the battery.
All that doesn't mean the hybrid battery is okay, but it's best to eliminate the simplist this first. And least expensive.

Autozone does NOT know how to check the battery for the Prius, they do not! You MIGHT get lucky and someone
MIGHT understand, but doubtful. They just do a regular load test.

Go to Toyota and get the Toyota batter for your car. Then CHARGE it! The batteries sit on a shelve and they do
NOT charge them. They slowly discharge over time and likely will be weak. Get a $10-15 Volt-Ohm-Meter and
check the voltage on the 12v battery. You can go to walfart and meter and get a 4 amp AGM charger for about $30-40.
After charging the battery for at least 4 hours, 6-8 would be better, remove the charger, wait 15 minutes or so and
check the voltage. It will be higher.
If the battery is 12.5 or less, it's weak. After charging, it will likely be 12.8 or above.
Reading your first post, it sounds like the 12v battery if old and weak and should be replaced.