engine light on ?

Hi
I HAVE A TOYOTA COROLLA VIDA REG. NO W153GGS MILAGE 91000
THE ENGINE LIGHT CAME ON AND I TOOK IT TO TOYOTA MAIN DEALERS CURRIES ISLEWORTH AND ON BOTH TIMES THEY TOLD ME THAT THERE ARE NO FAULT CODES RECORDED SO NO FAULT CODES WHY THE LIGHT GOES OUT AFTER 50 MILES AND THEN COMES ON? IF THEY CANT FIND ANY FAULTS AND THEY ALSO TOLD ME TO CARRY ON DRIVING IT MIGHT GO OFF FOR GOOD ON A SHORT TRIP IT WENT OUT GREAT I SAID AND WOULD YOU BELIEVE IT CAME ON AFTER ABOUT 2 MILES
Car has had a MOT ON 5TH NOVEMBER NO BAD EMISSIONS AND PASSED WITH COLOURS
HAVE TRIED TAKEN NEGATIVE LEAD FOR 10 MINUTES OFF THE BATTERY No luck
REMOVE THE FUSE No luck
CHANGE THE FUEL No luck
HAD THE SENSOR CLEANED IN THE MAF no luck
AA CHECKED AND NO FAULTS

WHAT ON EARTH CAN THIS LIGHT BE ON FOR WHEN THERE ARE NO FAULTS
CAN I TAKE THE LIGHT OFF

BEST REGARDS ROY