P0306
Fix within a few daysThe engine's computer has detected that cylinder number 6 is not firing correctly or is misfiring.
Code P0306 means Cylinder 6 is misfiring. Common causes: Ignition coil (40%), spark plug (30%), fuel injector (15%). Drivability: Yes, for short trips only. Repair cost: $50-$200 DIY, $150-$500 professional.
Can I Drive With P0306?
Yes, for short trips only
Essential trips under 10 miles, avoid highways. If the Check Engine Light is flashing, stop driving immediately.
Stop driving immediately if: Flashing Check Engine Light, loud knocking noises, burning smell, rotten egg smell from exhaust, significant power loss or engine shaking.
Symptoms of P0306
- 1Check Engine Light is on or flashing
- 2Engine runs rough or idles poorly
- 3Loss of engine power
- 4Engine hesitation or stumbling during acceleration
- 5Reduced fuel economy
- 6Strong smell of raw fuel from the exhaust
Common Causes of P0306
Parts most likely causing this code, ranked by probability
A faulty ignition coil fails to provide sufficient spark to ignite the fuel-air mixture in cylinder 6.
40% of P0306 cases are fixed by replacing this part
A worn, fouled, or damaged spark plug cannot create a strong enough spark for proper combustion in cylinder 6.
30% of P0306 cases are fixed by replacing this part
A clogged or faulty fuel injector fails to deliver the correct amount of fuel to cylinder 6, causing a lean or rich misfire.
15% of P0306 cases are fixed by replacing this part
Low compression in cylinder 6, due to issues like worn piston rings, burnt valves, or a blown head gasket, prevents proper combustion.
10% of P0306 cases are fixed by addressing this issue
A vacuum leak near cylinder 6, damaged wiring to the coil or injector, or a rare Powertrain Control Module (PCM) fault can cause a misfire.
5% of P0306 cases are fixed by addressing these issues
Check These First (Before Buying Parts)
- Visually inspect the ignition coil and spark plug wire (if applicable) for cylinder 6 for any cracks, burns, or loose connections.
- Listen for any obvious vacuum leaks around the intake manifold near cylinder 6 while the engine is running.
How to Diagnose P0306
- 1Connect an OBD-II scanner to confirm P0306 and check for any other related codes.
- 2Visually inspect the ignition coil and spark plug wire (if applicable) for cylinder 6 for any obvious damage or loose connections.
- 3Swap the ignition coil from cylinder 6 with a known good coil from another cylinder (e.g., cylinder 4 or 5). If the misfire moves to the new cylinder, the coil is faulty.
- 4If the misfire does not move, swap the spark plug from cylinder 6 with a spark plug from another cylinder. If the misfire moves, the spark plug is faulty.
- 5If the misfire persists, use a mechanic's stethoscope to listen to the fuel injector on cylinder 6. Compare its clicking sound to other injectors. A quiet or absent click indicates a faulty injector. You can also swap the injector with another cylinder to see if the misfire moves.
- 6Perform a compression test on cylinder 6. Compare the reading to the manufacturer's specifications and other cylinders. Low compression indicates an internal engine issue.
- 7Check for vacuum leaks around the intake manifold near cylinder 6 using a smoke machine or by spraying carb cleaner (carefully) around the area and listening for engine RPM changes.
P0306 on Popular Vehicles
Honda Accord
2003-2024P0306 on Honda Accords is frequently caused by a failing ignition coil or a worn spark plug. These components are accessible and relatively straightforward to replace.
70% fixed by Ignition Coil or Spark Plug
Ford F-150
2004-2024Ford F-150s, especially with V8 engines, are known for ignition coil failures. The coils are often exposed to heat, leading to premature failure. Spark plugs can also be a common culprit.
70% fixed by Ignition Coil or Spark Plug
Toyota Camry
2007-2024For Toyota Camry models, P0306 is typically resolved by replacing the ignition coil or spark plug for cylinder 6. Fuel injector issues are less common but still possible.
70% fixed by Ignition Coil or Spark Plug
Frequently Asked Questions
What does P0306 mean?
P0306 indicates that the engine's computer has detected a misfire specifically in cylinder number 6. This means cylinder 6 is not contributing its full power to the engine's operation.
Can I drive with P0306?
Yes, for short trips only, but you need to fix it quickly. If the Check Engine Light is flashing, stop driving immediately. Continued driving with a misfire, especially a severe one, can cause serious and expensive damage to your catalytic converter.
Will P0306 clear itself?
No, P0306 will not clear itself. The underlying issue causing the misfire must be identified and repaired. Once the repair is complete, you can clear the code with an OBD-II scanner, or it will clear itself after several drive cycles if the problem is resolved.
How do I fix P0306 myself?
Start by swapping the ignition coil from cylinder 6 with another cylinder. If the misfire moves, replace the coil. If not, swap the spark plug. If still no change, consider checking the fuel injector or performing a compression test. These steps often pinpoint the problem.
How much does it cost to fix P0306?
DIY repair costs for P0306 typically range from $50 to $200, depending on whether you need a spark plug, ignition coil, or fuel injector. Professional repair at a shop will cost between $150 and $500, including diagnosis and labor.
P0306 keeps coming back - why?
P0306 keeps coming back because the root cause was not fully addressed. This often happens if you replaced a part (like a coil) but the actual problem was something else (like a faulty spark plug, fuel injector, or even low compression). A thorough diagnostic process is essential to avoid repeat repairs.
Will P0306 fail emissions/smog test?
Yes, P0306 will cause your vehicle to fail an emissions or smog test. A misfire indicates incomplete combustion, leading to increased pollutants in the exhaust. The Check Engine Light being on or flashing is an automatic failure.
What's the difference between P0306 and P0300?
P0306 specifically indicates a misfire detected in cylinder number 6. P0300, on the other hand, means a 'Random/Multiple Cylinder Misfire Detected,' indicating misfires are occurring in multiple cylinders or are moving between cylinders, making it harder to pinpoint a single faulty component.
P0306 on Honda Accord?
P0306 on a Honda Accord often points to a failing ignition coil or spark plug for cylinder 6. Honda engines are generally reliable, but coils and plugs are common wear items. Start with swapping the coil and plug to diagnose.
Questions to Ask Your Mechanic
Did you perform a cylinder balance test or a power contribution test to confirm the misfire on cylinder 6?
Good answer: Yes, the scan tool confirmed cylinder 6 is consistently dropping out. We also checked the fuel trims.
What were the results of the compression test on cylinder 6 compared to the other cylinders?
Good answer: Cylinder 6 showed 180 PSI, which is consistent with the other cylinders and within specification. Compression is good.
Did you check the fuel injector's pulse and spray pattern for cylinder 6?
Good answer: Yes, we checked the injector pulse with a noid light and confirmed it's getting signal. We also removed and tested the injector for proper spray pattern and flow.
Repair Cost Estimate
DIY Repair
Parts only
$50-$200
Shop Repair
Parts + labor
$150-$500
Save $100-$300 by doing it yourself
Difficulty
intermediate
Time
0.5-2 hours
Intermediate. Swapping an ignition coil or spark plug is manageable for many DIYers, but diagnosing fuel injector issues or low compression requires more specialized tools and diagnostic skills.
Cost of Waiting
Continued misfires send unburned fuel into your exhaust system, causing your catalytic converter to overheat and fail. A $50 spark plug or $100 ignition coil job now prevents a $800-$2,500 catalytic converter replacement later.
While You're In There...
If you're replacing the ignition coil, it's smart to replace the spark plug at the same time. They wear together, and you're already accessing the cylinder.
If your vehicle uses separate coil boots, replace it when changing the coil or plug. They can crack and cause spark to arc, leading to misfires.
Apply dielectric grease to the spark plug boot and coil connector to prevent moisture intrusion and ensure good electrical contact.
Tools You'll Need
- OBD-II scanner
- Spark plug socket set (with extension and swivel)
- Ratchet
- Torque wrench
- Screwdrivers or wrenches (for coil/injector removal)
- Dielectric grease
- Compression tester (if needed)
- Fuel injector test light (noid light) (if needed)
P0306 is a very common engine code. Most repairs are straightforward, involving replacing a single component, and your engine will run smoothly again once fixed.
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Your Next Steps
Step 1: Use an OBD-II scanner to confirm P0306 and check for any other codes. Note if the Check Engine Light is flashing.
Step 2: Swap the ignition coil from cylinder 6 with a coil from a different cylinder. If the misfire code moves to the new cylinder, replace the ignition coil.
Step 3: If swapping the coil doesn't fix it, swap the spark plug from cylinder 6 with a plug from another cylinder. If the misfire moves, replace the spark plug. If the misfire persists, you'll likely need to investigate the fuel injector or perform a compression test.