If an emission-related fault is detected, the Diagnostic Executive will activate the MIL and allow it to remain "on" until the system or component passes the same test for three consecutive trips without the fault reoccurring.
MIL On Or Flashing - Fuel System Or Misfire Conditions:
If a Fuel system problem or misfire condition is present that could damage the catalyst, the MIL will flash once per second. The MIL will continue to flash until the vehicle is outside of the speed and load conditions that could cause possible catalyst damage. It will stop flashing and remain on once these conditions: are no longer present.