If your vehicle is showing check engine light is flashing, here are the most likely causes and the parts you'll need to fix each one.
Spark plugs wear out over time, leading to a weak spark or no spark at all. A flashing check engine light indicates a severe engine misfire that can damage the catalytic converter, often caused by these worn plugs.
Ignition coils generate the high voltage needed to fire the spark plugs. When a coil fails, its corresponding cylinder goes completely dead, resulting in a heavy misfire and a flashing warning light.
If spark plugs were recently replaced, the ceramic insulator may have been accidentally cracked by the socket, or a coil connector was left unplugged. This causes an immediate, severe misfire upon startup.
On vehicles equipped with them, spark plug wires break down from engine heat and age. This allows the electrical spark to arc to the engine block instead of reaching the spark plug.
A massive unmetered air leak, such as a torn PCV hose or a blown intake manifold gasket, drastically throws off the air-fuel ratio. This can cause multiple cylinders to misfire simultaneously.
If a fuel injector fails electrically or becomes completely clogged, the cylinder receives no fuel. This creates a lean misfire that triggers the flashing check engine light.
A burnt engine valve, blown head gasket, or damaged piston rings will cause a permanent loss of cylinder compression. This results in a continuous, catastrophic misfire that requires major engine repair.