Summary
P0306 means the PCM detected repeated misfires in cylinder 6. This code appears only on 6+ cylinder engines. The diagnostic approach is identical to other single-cylinder misfire codes: coil-swap test first, then spark plug, fuel injector, and compression. On V6 engines, cylinder 6 is typically the last cylinder on Bank 2 — often in a harder-to-reach location near the firewall.
Severity: Moderate to High — misfires damage catalytic converters
Safe to drive: Not recommended
Repair cost: $20–$500 depending on cause
DIY difficulty: Easy to Moderate
What does P0306 mean?
The PCM detected that cylinder 6 is consistently misfiring. On most V6 engines, cylinder 6 is on Bank 2, often the rearmost cylinder closest to the firewall. On inline-6 engines, it's the last cylinder. This position can make spark plug and coil access more difficult, but the diagnostic logic is the same as any single-cylinder misfire.