2000 Other Saturn Models 2000 SATURN LS1

I HAVE A 2000 SATURN LS1 THAT DIED AT THE STOP SIGN.THE CAR WAS RUNNING GREAT AND IT HAS GIVEN ME NO PREVIOUS TROUBLES WHATSOEVER. THE ENGINE WILL CRANK, BUT WONT START. I CHECKED TO MAKE SURE IT WAS GETTING FUEL, AND IT IS. I HAVE REPLACED THE IGNITION CONTROL MODULE, CRANKSHAFT POS. SENSOR, SPARKPLUGS BUT STILL NO LUCK. COULD IT BE THE TIMING CHAIN? ALSO, THERE IS A BLACK BOX UNDER THE DRIVER'S SEAT WHICH SOMEONE SAID MAY BE BAD. I DON'T KNOW WHAT THIS PART IS, HOWEVER. I PLUGGED AN OBD2 INTO THE COMPUTER, BUT THERE ARE NO CODES IN THE SYSTEM. ANY SUGGESTIONS? THANK YOU SO MUCH.