it means stop driving the car...
when it flashes there is a major problem meaning the converter is in danger of destruction..im telling you that you have a misfire and you definately do..
it needs to go to a reputable shop if you cant get ahold of a scanner to read the
codes stored..do not drive around go to your destination and stay there..
flashing light basically means that there is unburnt fuel coming into the converter.
because a cylinder is not firing through the plug..you either got a bad coil,
cracked plug, the wrong plug, crossed plug wires, bad wire, wire arcing on metal.
plug boot not set properly (happens with cheap wires)..
i have even seen a new sparkplug electrode drop onto the tab causing no gap..
you need to recheck everything, have a cylinder balance test done,
or get a spray bottle and spray around the ignition system with the car running
to check for arcing wires, boots or coil.. spray and if the car runs worse almost instantly...you have an ignition problem or (misfire)..