P0306: Cylinder 6 is misfiring
Cylinder 6 Misfire Detected
Cylinder 6 is misfiring. If the light is flashing, stop driving. If it is steady and the car shakes, get it checked today. A misfire can destroy the catalytic converter.
Stop driving and get help if
- The check engine light is flashing
- The temperature gauge runs high, or you see steam (overheating)
- The car loses power, hesitates badly or stalls
- You smell burning or see smoke
- A brake warning light comes on, or the brakes feel different
Pull over as soon as you can, turn the engine off, and call a tow or roadside help.
What it means
P0306 means cylinder 6 is not completing combustion reliably. Cylinder 6 exists on V6, V8, and larger engines. On a V6, cylinder 6 is at the rear of Bank 2, which is often near the firewall on front-wheel-drive vehicles. Accessing cylinder 6 on a transversely mounted V6 can be genuinely difficult and is where labor costs climb for what would otherwise be an inexpensive ignition repair. On V8 engines, cylinder 6 is typically the second from the rear on one bank and is somewhat more accessible than cylinder 8.
Common causes
- Failed ignition coil on cylinder 6Coil failure is the leading cause. Swap and road test to confirm before buying a part.
- Worn spark plug on cylinder 6On transverse V6 engines, rear-bank plugs are often skipped at service intervals due to access difficulty.
- Failed or clogged fuel injector on cylinder 6Check for P0206 in the stored codes.
- Low compression on cylinder 6More common at high mileage. Compression test required.
- Water or carbon in the intake on cylinder 6Direct-injection engines accumulate carbon on intake valves, causing intermittent lean misfires.
What the fix could involve
From the cheaper fix to the bigger one. Prices depend on your car, your area and the shop, so ask for a written quote that names the part and the labor before you approve it.
- Spark plug set
- Ignition coil (one)
- Fuel injector (one)
- Compression repair
Symptoms
- Check engine light flashing or steady
- Engine vibration at idle and low speed
- Hesitation or stumble on acceleration
- Power loss
- Possible fuel smell from exhaust
What to do next
Get a labor estimate before you start if your V6 has rear-bank access issues. On some vehicles (Chrysler 3.5L, GM 3.6L), replacing rear-bank spark plugs requires removing the intake manifold, so labor alone can be costly. Confirm the diagnosis with a coil swap before committing to full spark plug replacement if the car is a known difficult-access engine.
Lewis reads P0306 alongside any other misfire codes, stored or pending, so you can see whether the misfire keeps coming back after a fix. Get Lewis on the App Store or Google Play.
Related codes
FAQ
- Why is cylinder 6 more expensive to fix than cylinder 1?
- Access. On many transverse V6 engines, cylinder 6 is behind the engine near the firewall. Reaching the spark plug or coil requires significant disassembly.
- Can P0306 on a V6 be a valve cover gasket leak?
- Yes. Oil leaking from the valve cover gasket into the spark plug well can short out the coil and foul the plug, both causing a misfire on that cylinder.
- Should I replace all six plugs or just the one on cylinder 6?
- If mileage is high and plugs have not been done, replace all of them while you have access. One failed plug often means the others are not far behind.
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