Let’s try again!

how many miles on her?

 

nice, i guess you can expect brake issues by then. when lights are on, there are codes. are you using tech stream to read them?

 

could just be frozen, but before you take anything apart, always disconnect the 12 volt battery.

 

How did you determine that the one brake was not working? My understanding (which is somewhat limited) is that the actual mechanichal braking only happens when the Prius is traveling very slowly.

That question aside, based on what you have written I'd take a close look at the wheel cylinder.

I DIYed the rear brakes on my newly acquired 240k mile, '05 a few months ago. I bought the car from a relative for short money because the brakes were in such terrible condition and raising a huge racket.

I ended up changing both rear brake wheel cylinders as a visual inspection revealed the seals were shot and leaking. I did the rears about 2 weeks after doing the fronts. Before I did the rears I thought the car stopped pretty well but I only drove it about 100 miles or so with no hard stops.

So I did the rears, changing the shoes, drums, hardware, springs and wheel cylinders. Then I went to a dealer to have the brakes bled. This was essential after removing the wheel cylinders which, of course, opens the brake lines.

(I suggest that if you do this that you use liberal amounts of PB blaster and turn the cylinder itself while holding the brake line nut rather than turning the brake line nut which will likely collapse the brake line.)

The other possibility I would check is air in the brake lines. If the wheel cylinders are leaking air could be getting in. Is the fluid resevoir full? Has the system been bled? My understanding of the Prius braking system is that the computerized braking can mask air in the line. Peddle might feel OK but localized air pockets might exist. You'll need to go to a specialist or dealer to get the brakes bled.