🔥 Engine Misfire Codes
TL;DR
Misfire codes (P0300 random, P0301–P0304 per cylinder) mean a cylinder is not firing right. Severity: medium — high if the light is FLASHING (stop driving, the catalytic converter is at risk). Top causes: worn spark plugs, failed ignition coils, then injectors or a mechanical (compression) fault.
Codes in this family
Shared causes
- Worn or wrongly gapped spark plugs (most common)
- A failed ignition coil (often a single-cylinder code)
- A clogged or leaking fuel injector
- Vacuum leak or lean condition
- Mechanical fault — low compression (valve, rings, head gasket)
Parts commonly involved
Related symptoms
Frequently asked questions
What does the cylinder number in a misfire code mean?
The last digit tells you the cylinder: P0301 is cylinder 1, P0302 is cylinder 2, and so on. P0300 means a random or multiple-cylinder misfire with no single cylinder identified.
Is it the spark plug or the coil?
Swap the coil from the misfiring cylinder to another. If the misfire follows the coil, the coil is bad; if it stays, suspect the plug, injector or compression. Plugs are cheap, so many people replace both.
Why is a flashing check engine light urgent with a misfire?
A flashing light means an active misfire dumping raw fuel into the exhaust, which overheats and can destroy the catalytic converter. Stop driving and fix the misfire before it turns a cheap repair into an expensive one.