Cylinder 6 Misfire Detected
P0306 indicates that the engine control module (ECM) has detected a misfire in cylinder 6. A misfire occurs when the air-fuel mixture in the cylinder fails to ignite properly, causing a loss of power, increased emissions, and potential damage to the catalytic converter. Common causes include faulty spark plugs, ignition coils, fuel injectors, or low compression. This code is often accompanied by rough idling, hesitation, and the check engine light.
01. Most Common Causes
- Faulty spark plug or ignition coil on cylinder 6
- Clogged or leaking fuel injector on cylinder 6
- Low compression due to worn piston rings, valves, or head gasket
- Vacuum leak or intake manifold gasket leak
- Engine control module (ECM) or wiring issue
02. Symptoms You Will Notice
- Check engine light illuminated
- Rough idle or engine shaking
- Loss of power or hesitation during acceleration
- Increased fuel consumption
- Engine may run rough or stall
03. Step-by-Step Diagnosis
Step 1: Scan for codes and verify P0306 is present. Check freeze frame data for conditions when misfire occurred.
Step 2: Inspect spark plug and ignition coil on cylinder 6. Swap coil with another cylinder to see if misfire moves.
Step 3: Test fuel injector on cylinder 6 for proper spray pattern and resistance. Perform a cylinder contribution test.
Step 4: Perform a compression test on cylinder 6 and compare to other cylinders. Check for vacuum leaks using a smoke machine.
Step 5: Inspect wiring and connectors to the injector and coil. If all else fails, consider ECM issues.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances with a misfire as it can damage the catalytic converter and other engine components. Short trips to a repair shop are acceptable if the engine is not overheating or severely shaking.
How much does it cost to fix?▼
The cost varies depending on the cause. Replacing a spark plug or ignition coil typically costs $50-$150 per part plus labor. Fuel injector replacement can be $150-$400. Compression repairs can be significantly more expensive.