Parts
$8–120
P0306 — Cylinder 6 Misfire Detected
CAUTIONIs it safe to drive? Same as any single-cylinder misfire — drivable short-term, but a flashing CEL means pull over; sustained misfiring melts catalytic converter bricks.
What P0306 means
Cylinder 6 is firing inconsistently or not at all. On V6/V8 engines cylinder 6 is often on the firewall side, making it harder to reach, but the diagnosis steps are identical to any other cylinder.
Most likely causes (in order)
- Spark plug fouled or worn out
- Coil-on-plug unit for cyl 6 (swap-test before buying)
- Fuel injector — spray pattern or dead driver
- Valve cover gasket leaking oil onto plug or boot
- Low compression (rings, valve, or head gasket)
Symptoms you might notice
- rough idle
- vibration at idle
- poor fuel economy
- hesitation under load
- flashing CEL
What to check first
Pull the cylinder 6 plug and inspect it: oil-fouled means a leaking valve cover gasket or piston rings; fuel-soaked means injector stuck open; white/gray deposits mean normal wear. The plug tells the story before you replace anything.
Repair cost & difficulty
Labor
0.5–2 hr
Difficulty
DIY-friendly