If your vehicle is showing check engine light is flashing while driving, here are the most likely causes and the parts you'll need to fix each one.
The most common cause of a flashing check engine light is a severe engine misfire due to worn out spark plugs or a failed ignition coil. This dumps unburned fuel into the exhaust, which can rapidly destroy the catalytic converter.
If work was recently done under the hood, a spark plug may not be torqued correctly, or an ignition coil connector might be loose or swapped. This causes an immediate misfire.
A bad fuel injector can either starve the cylinder of fuel or stick open and dump too much fuel in, causing a severe misfire that triggers the flashing light.
A cracked intake manifold gasket or broken PCV hose can let unmetered air into the engine, causing a severe lean misfire across one or multiple cylinders.
A burnt engine valve, blown head gasket, or broken valve spring will cause a dead cylinder and constant misfire. This is a catastrophic failure requiring major internal repair.