my check engine light is flashing on and off. what does that mean?

my check engine light been on for 3yrs now n still no problems,

It means damage to your catalytic converter is occuring. If your car is running rough and has no power, check your crank position sensor before you dump a bunch of time and money in it.

On Mazda's, when the check engine light is flashing it means you have a misfire. The most common causes are the ignition coil packs or spark plugs.

I changed the sparks plugs . And it runs better but still the engine light is still doing the same thing