see
SSC 60G 2001 THROUGH EARLY 2002 ECHO AND PRIUS CRANKSHAFT POSITION SENSOR
2001 through early 2002 model year Toyota ECHO and Prius vehicles
Toyota will initiate a Special Service Campaign to replace the Crankshaft Position Sensor on 2001 through early 2002 model year ECHO and Prius vehicles.
In certain 2001 through early 2002 model year ECHO and Prius vehicles, the connector for the Crankshaft Position Sensor may become disconnected. In the worst case, if the Crankshaft Position Sensor becomes disconnected while the vehicle is being driven, the engine will stall and will be unable to restart.