The engine management lamp comes on when a fault develops in the engine fuel, ignition or emission systems.  At this stage its impossible to tell why, but a 'fault code' is stored in the car's on board computer, and this can be interrogated by any garage with suitable diagnostic equipment.  They can then recommend a repair, and turn the light back off for you.  Take a tip....if you let a fault continue there is a chance that the catalytic converter could be damaged - quite expensive.
                 John
                
 January 2008