Check engine light 2002 prius
 

About once a month, 1500 miles, the check engine light comes on and the engine dies after starting a warm engine. Engine has about 100K miles.
The engine needs to be started about 5 times to clear the video screen of warnings. Any ideas of what may cause this behavior? I have tried several different brands of regular gasoline. Problem occurs in both summer and winter, but never when the engine is cold.