The check engine light is designed to turn on when there is a fault in your vehicle systems. When it blinks the fault has become detrimental enough to cause damage to the catalytic convertors. Most often the light will blink due to a misfire significant enough to cause excess amounts of fuel to dump into the exhaust system. This excess amount of fuel is then burned in the catalytic convertors causing them to superheat. This can cause the substrate in the convertors to melt which will completely ruin the convertors. Due to the expensive metals that are used in the catalytic convertor this can be a very costly repair. The sooner the misfire is corrected, the more money you can save in other repairs that can be avoided by not procrastinating.