I changed the battery and upon starting it back up, as soon as I press the brake pedal it began to beep, constantly, just bee- etc. And the brake pedal was extremely hard to push and was very sensitive. And the BRAKE light is on, the VSC is on, and the ABS is on, I've looked and looked for answers on this and I've found similar problems but never this exact one.
Yes ABS actuators gonna be showing codes . Probably for low accumulator pressure Read the codes you will see this is very common especially at this age this model year etc It seems to be very normal You need a break actuator.
First thing to do is just get the codes. It's easy and saves all the speculation in advance about what codes you "probably" have or don't have. Just find out what codes you do have, and we can go from there. Find out this way: Blink (a/k/a Flash) Codes – How to. | PriusChat
I'll assume you replaced the 12v aux battery in the rear of the car. When replacing the 12v battery in a Gen 2, many people disconnect and remove the brake backup power supply box that is located directly to the inside of the 12v battery. It allows more room for removal/installation. If the problems you're currently experiencing are new, the first thing I would do is ensure I mounted and reconnected that box correctly.
