One problem related to brake antilock wheel speed sensor has been reported for the 2005 Toyota Prius. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2005 Toyota Prius based on all problems reported for the 2005 Prius.
While I was driving down the street, suddenly an abs warning light and a beeping sound engaged. To investigate the abrupt occurrence I attempted to pull over. However as I applied my brakes they wouldn't work. My brakes completely failed. I'm extremely fortunate that I was afforded the distance to allow my car to slow down on its own. To make a complete stop I applied my parking bake. I was lucky to avoid crashing into the car just feet in front of mine. I can only imagine the devastation if this was to happen on a busy intersection or a freeway off ramp. Thankfully, there are no injuries to report. My car is currently at a dealer/service center. They said the brake actuator and speed sensor needs to be replaced. I've opened a case with Toyota to investigate the failure.