P0306: Cylinder 6 Misfire Detected
Updated November 12, 2026
Cylinder 6 isn't firing properly. The engine computer detects this as a small slowdown in crankshaft speed each time that cylinder should fire. It only applies to engines with six or more cylinders.
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🔧 Want to check this yourself? An OBD2 scanner reads the code; models with live data also show the sensor readings used in the checks below. See code readers and scanners from $24.99 ↓ · Which scanner do I need?
Common causes
- A worn spark plug in cylinder 6
- A failing ignition coil or plug wire
- A clogged or leaking fuel injector
- A vacuum leak near cylinder 6
- Low compression (valve, ring or head gasket problems)
Code meanings can vary slightly by manufacturer. Use these as a starting point and confirm with your vehicle's service information or a mechanic before replacing parts.
Symptoms
- Rough idle or a shake at stops
- Hesitation or loss of power
- Flashing check engine light under load
- Fuel smell from the exhaust
Is it safe to drive?
Avoid hard acceleration and get it fixed soon. A flashing check engine light means the misfire is bad enough to damage the catalytic converter.
How to check it with a scanner
- Plug an OBD2 scanner into the port under the dashboard and read all stored codes and the freeze-frame data (the conditions when the code set).
- Confirm where cylinder 6 is on your engine; on V6 and V8 engines numbering differs between makers.
- Swap the coil (and if easy, the spark plug) with another cylinder and see whether the misfire follows the part.
- If the ignition parts check out, test the injector and run a compression or leak-down test.
- After a repair, clear the code and drive normally for a few days to confirm it doesn't come back.
A basic code reader shows the code; scanners with live data let you watch sensor readings, which is what you need for most of the checks above. See OBD2 scanners under $100.
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Questions
What does P0306 mean?
P0306 is the generic OBD2 code for "Cylinder 6 Misfire Detected." Cylinder 6 isn't firing properly. The engine computer detects this as a small slowdown in crankshaft speed each time that cylinder should fire. It only applies to engines with six or more cylinders.
Is it safe to drive with P0306?
Avoid hard acceleration and get it fixed soon. A flashing check engine light means the misfire is bad enough to damage the catalytic converter.
How do I check P0306 myself?
Read the code and freeze-frame data with an OBD2 scanner, then: Confirm where cylinder 6 is on your engine; on V6 and V8 engines numbering differs between makers. Swap the coil (and if easy, the spark plug) with another cylinder and see whether the misfire follows the part. If the ignition parts check out, test the injector and run a compression or leak-down test.
Related codes
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