P0306: Cylinder 6 Misfire Detected

What does P0306 mean?

Misfires are isolated to cylinder 6. On V6 engines this is commonly on the rear bank near the firewall, the hardest cylinder to service. On inline-six engines it's usually the cylinder at the transmission end. Because access is difficult, it's worth confirming the cause before you start removing parts.

Generic OBD-II definition: Cylinder 6 Misfire Detected. Confirm applicability in your vehicle service information.

Common causes

• Rear-bank spark plug past its service life
• Rear-bank ignition coil weakened by heat
• Cylinder 6 injector failing
• Oil or coolant getting into the cylinder (for example from a leaking intake gasket)
• Low compression in cylinder 6

Symptoms

• Rough running that is noticeable at idle
• Hesitation under load
• Lower fuel economy

Can I keep driving with P0306?

Severity: High Stop or minimize driving and get it looked at right away.

If the check engine light is flashing or the car runs badly, stop driving and have it checked.

Typical fixes

• Use a scanner's misfire counters to confirm only cylinder 6 is counting misfires
• Swap cylinder 6's ignition coil with a neighboring cylinder's coil, clear codes, and drive: if the code moves to that cylinder, the coil is bad
• Inspect the plug for coolant residue (white, clean deposits), which can point to a gasket leak
• Compression-test cylinder 6 if the misfire doesn't follow the coil or plug