A flashing check engine light is not the same as a steady one. Flashing means the engine is actively misfiring right now - and every minute you keep driving risks destroying your catalytic converter, which costs $800-$2,400 to replace. Pull over when it's safe and get this diagnosed before driving further.
P0300 means multiple cylinders are misfiring simultaneously. Unburned fuel enters the exhaust and can overheat your catalytic converter within minutes of driving.
View Full Diagnosis - P0300 →A cylinder-specific misfire (P0301 = cylinder 1, P0302 = cylinder 2, etc.) means one cylinder has stopped firing. Same cat-damaging risk applies.
View Full Diagnosis - P0301 →P0420 can appear alongside a misfire if the cat has already been damaged. Usually a steady light for this code, but occasionally flashing during active damage.
View Full Diagnosis - P0420 →Same as P0420 but on the passenger-side bank of V-engines. Appears when Bank 2 catalytic converter is failing or has been damaged by misfires.
View Full Diagnosis - P0430 →Enter it below for a free diagnosis. You'll get the most likely cause instantly - no account needed.
Get Free DiagnosisDon't have a scanner? Most AutoZone and O'Reilly locations read codes for free.
If your scan tool is showing one of these codes alongside a flashing check engine light, that's your starting point. Click any code for the full diagnosis, common causes, and repair costs.
No - stop as soon as it's safe. A flashing light means an active misfire sending unburned fuel into your exhaust. This can overheat and destroy your catalytic converter within a few miles of driving. A steady check engine light is very different and generally safe to drive with short-term.
Almost always a cylinder misfire. Misfires happen when a spark plug, ignition coil, fuel injector, or compression is not working correctly on one or more cylinders. The ECU triggers a flashing light specifically because catalyst damage is imminent.
It means the active misfire has stopped, but the underlying cause is still there. The code is stored in memory. You should still diagnose it today - the misfire can return at any time, and driving with a stored misfire code can eventually lead to the same cat damage.
It depends on the cause. Spark plugs cost $20-80 to replace yourself. Ignition coils are $30-80 each. Fuel injectors are $50-150 each. Catalytic converter replacement - if you drove on it too long - runs $800-$2,400. Diagnosing the code first prevents replacing the wrong part.