the engine management light is telling you that the e c u has picked up a fault somewhere in the system. so it needs to be plugged into a diagnostic computer, the e c u will then tell the computer whatever the fault is. your car may be running o.k. but the e c u has picked up on a fault somewhere ( probably in the ignition system or fuel system ).
you may be able to make the engine management light go out by disconnecting the car battery for about 10 mins and then reconnecting it, this reboots the system.