One problem related to brake hoses, lines/piping, and fittings has been reported for the 2004 Toyota Prius. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2004 Toyota Prius based on all problems reported for the 2004 Prius.
Recently, I performed a routine flush of the brake fluid on my Toyota Prius. When I started the Prius after completing the brake fluid flush, there were warning lights showing on the dashboard for the brakes, the traction control system, and the anti-lock brake system. This didn't surprise me that the car detected an abnormality during the brake bleeding operation. What did surprise me is that the Prius computer instructed the front brakes to become non-operational the trouble code in the Prius computer automatically disabled the front brakes because the computer was confused by the varying pressures present in the brake lines during a routine brake fluid flush. I drove to a repair shop with only the rear brakes operational. At the repair shop, a technician cleared the trouble codes for the brake system stored in the electronic control module of the Prius. The brakes were then completely operational. I find it unconscionable that the car could decide on it's own to disable the brakes, even when the brakes were otherwise fully functional. Please require Toyota to program their control modules to allow the brakes to function when trouble codes are activated.