I have a 2007 base model prius with 122k on the car. it has had little to no issues, about 2 weeks ago when I start my car a loud alarm is going off and while the alarm is on I have very limited breaking ability. the breaks are about 20% effective ant the break pedal is hard to press. the abs and vsc lights came on a few days in to this issue. next the entire dash display quit lighting up and comes back on after restarting the car several times. next the emergency (!) symbol appeared today. what is going on and how did the car go from perfect to crap in under 3 weeks with light use (to and from work only). after the vsc light came on acceleration is not normal and starting movement after stopping at a light is the worst. in addition when I hold the breaks like for a light or traffic a weird clicking sound and vibration comes from the breaks. I took it to a hybrid mechanic (non-dealer) he couldn't pin point it but said it would be in the area of $1,800 to fix it????
Sounds like the brake AbS unit has failed. There was a TSB out for the last year but I think I its over. Get to the dealer see if they will offer any good will on it. Search Brake abs in search forum button on top of page. Very common.
In a Gen 2, most of the parts (except for some wires/connectors/fuses/relays) that could be at fault are in the single "brake actuator assembly". So there's a good chance it's that, unless you have a simpler problem involving a flaky connector, etc. So there are a couple different styles of diagnosis you can follow: A. You see that the actuator assembly is expensive and a PITA to replace, so before you do that, you want to rule out the other possibilities. So you read the trouble codes the car is trying to give you, look them up in the Repair Manual (more info), and follow the workup steps, and solve the simpler problem if there is one, or replace the actuator if that's where the workup steps lead you. B. You see that the actuator assembly is often the culprit, so you shell out the bucks and do the PITA replacement, betting that it may well solve your issue, and if it doesn't, well, then you'll go back and do the stuff you'd have done first in style A. Either approach will solve your problem (eventually).