Mil Illumination
WARNING: This page is about a different car, the 2004 Kia Rio. However, it is still accessible from the selected car via links, so may be relevant.
The MIL is illuminated when a misfire is detected which can cause the damage of catalyst or exhaust emission higher than 1.5 times certification standard (I/M failure).
The MIL flashes while a catalyst damaging misfire is being detected.