CarSense › Trouble codes › P0306

P0306: Cylinder 6 Misfire Detected

What this check-engine code means in plain English, what usually causes it, and what a fix typically costs.

Severity: Urgent — can cause catalytic converter damage and unsafe driving conditions

What P0306 means

The engine control module has detected that cylinder 6 is not firing properly or consistently. A misfire means the air-fuel mixture in that cylinder isn't igniting correctly, causing rough running, power loss, and potentially damaging the catalytic converter with unburned fuel.

What causes P0306?

Likely
Faulty spark plug or ignition coilWorn spark plugs or a failed ignition coil on cylinder 6 are the most common causes of single-cylinder misfires.
Likely
Fuel injector problemA clogged or failed fuel injector for cylinder 6 can prevent proper fuel delivery and cause misfires.
Possible
Low compressionWorn piston rings, valves, or a blown head gasket can reduce compression in cylinder 6, preventing proper combustion.
Less common
Vacuum leak or intake manifold gasketA vacuum leak affecting cylinder 6 can disrupt the air-fuel mixture and cause misfiring.

Is P0306 safe to drive?

Drive it?
Short distances only, gently
Watch for
Rough idle, shaking, loss of power, check engine light flashing
DIY-friendly?
Spark plug replacement is DIY-friendly; coil swapping for diagnosis requires moderate skill

You can drive short distances carefully to reach a repair shop, but continued driving with a misfire can damage the catalytic converter (expensive repair) and may cause the vehicle to shake violently or stall. If the check engine light is flashing, stop driving immediately as this indicates severe misfiring that can cause immediate damage.

P0306 repair cost

~$100 – $1000+

Industry-average estimates. Cost depends on the root cause—spark plugs are inexpensive while ignition coils, injectors, or compression issues cost significantly more.

Which one is it for your car?

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