Front Brake Caliper Piston stuck out

Get a rebuilt caliper or a seal kit and disassemble and repair. We use techstream to bleed the system, without it may be a pain

 

Not a Prius brake system expert as it is fairly involved but your up against a closed brake fluid metering solenoid. That's why you cant push the piston back.
With techstream your able to open and close the solenoids at will.

Sometimes just opening the door during a brake service will pop the piston out so it is very important that you disconnect the 12 volt battery then push the brake pedal a few times before re starting any brake service,
I would imagine you need to disconnect the 12 volt battery brake back up supply also which is the little black box next to the 12 volt battery. It has a lot of capacitors in it that hold a charge.

I think Travis is right once the piston is hyper extended it may damage the piston seal.

 

I potentially have the same problem here, but I'm not fully certain that the piston is out. How can one tell? I am changing the wheel bearing and got in the car and accidentally started it, not realizing about the brake issue (should have read more). The piston moved out enough to push the pad out, but I can't tell if the piston is out of its sleeve.

Also, if I were to open the solenoid using techstream (which i have), where can I find that in the software? Thanks!!

 

You should have brake fluid leaking if piston is out of sleeve...
I'm not too familiar with software, and not able to help you with that. But you could do it the old fashioned way, open the bleeding valve and press it back in and manually bleed any air out..

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