Draft guidance: awaiting Claude spot-check, qualified-mechanic review and named-editor approval. Do not use a fault code alone to replace parts.

P0306: Cylinder 6 misfire detected

The engine computer has detected an uneven contribution from cylinder 6.

What P0306 means

The engine computer has detected an uneven contribution from cylinder 6. It does not establish whether the cause is ignition, fuelling, an air leak or a mechanical engine fault. Cylinder 6’s position must be checked against vehicle-specific information.

Can I still drive?

A flashing warning light, strong shaking, stalling, fuel smell or serious loss of power calls for an immediate safe stop and recovery because continued misfiring can damage the catalyst. With a steady light and otherwise normal running, make only a short, low-load trip to a repairer and arrange prompt diagnosis.

Symptoms

  • Lumpy idle or vibration under acceleration.
  • Hesitation, reduced power and poorer economy.
  • Hard starting or stalling.
  • Unusual exhaust or raw-fuel smell.
  • Steady or flashing engine-management light.

Common causes

  • Worn or fouled spark plug.
  • Faulty coil, high-tension lead or boot.
  • Injector, injector wiring or local fuel-delivery fault.
  • Vacuum or intake leak affecting that cylinder.
  • EGR flow entering one runner unevenly on applicable engines.
  • Low compression or another valve, piston or timing-related problem.

Safe first checks

  • Record all codes and freeze-frame information, then verify cylinder numbering. With the engine cold and switched off, inspect cylinder 6’s plug well, coil or lead, injector connector and visible loom. Look for moisture, oil, corrosion, chafing and loose fittings. Check for companion lean, fuel-pressure, EGR or timing codes. Leave injector actuation, live ignition testing and compression testing to a competent technician.

Typical UK fix cost

Budget around £90–£180 for diagnosis. A plug or accessible coil fault commonly produces a total of about £130–£350; injector or wiring work may be £250–£700. Mechanical repairs can run from £700 to £3,000+, depending on access and damage.

Related models

This is a generic OBD-II code used across many makes and models. The exact test thresholds, component layout and repair route vary by engine and manufacturer, so check vehicle-specific technical information before ordering parts.

Related fault codes

Sources

A diagnostic trouble code identifies a system or circuit to investigate. It does not prove that a named part has failed. Preserve freeze-frame data and seek a vehicle-specific diagnosis before clearing the code.