The 2004 Toyota Prius has 9 recalls, the most serious involving the steering intermediate shaft, which can wear, crack, or separate over time and cause a complete loss of steering control.
Several of these recalls address the same steering shaft problem from different angles: the splines connecting the steering wheel to the steering gear can degrade with use, and the shaft sleeve can crack or pull apart under hard steering inputs, leaving the driver unable to steer the vehicle. On the powertrain side, the electric water pump that cools the hybrid system can fail or short-circuit, causing warning lights to appear and the engine to stall while driving. There is also a floor mat concern: if the driver's floor mat is not properly secured or is incompatible with the vehicle, it can trap the accelerator pedal wide open, making the car very difficult to slow down or stop. Rounding out the list, a residue buildup inside the brake light switch can make it stop working, so the brake lights fail to illuminate when the pedal is pressed, leaving following drivers with no warning that the car is slowing.