EngineLightCodes
Powertrain code

P0306 Cylinder 6 Misfire Detected

Severity
Stop soon
Typical repair cost
$30–$880
Do it yourself
Possible, easy
Shop time
0.3–4 hours

Cylinder 6 is misfiring: its fuel isn't burning properly on every stroke, which you feel as shaking, a rough idle or hesitation. You'll only see this code on engines with six or more cylinders. A worn spark plug or a failing coil on cylinder 6 is the most common reason.

How the engine computer detects it

The engine module detects misfire from crankshaft speed: a cylinder that does not fire gives no acceleration impulse. At a catalyst-damaging rate (CARB: at least 5 % per 200 revolutions) the warning light flashes; at an emissions-relevant rate (at least 1 % per 1,000 revolutions – GM about 2–5 %, Ford 0.9–1.5 %) it comes on after two trips. Ford and GM may shut off a misfiring cylinder's injector to protect the catalyst. P0306 means more than 90 % of the detected misfires fall on cylinder 6. Usual causes are the ignition coil or spark plug of that cylinder, its injector, or low compression; a quick test is to swap coil or plug with a neighbouring cylinder and see whether the misfire moves. GM found heat-damaged coils on its 3.6 V6 caused by a stuck ignition signal – the damaged coil need not be on the misfiring cylinder.

Written from public technical sources and not yet checked by a mechanic. How we write these pages

Symptoms

  • Check engine light on, flashing at a catalyst-damaging rate
  • Rough idle, jerking, vibration
  • Loss of power, hesitation
  • Smell of unburnt fuel, higher consumption

Common causes

  1. Ignition coil of cylinder 6 faulty (coil, connector, ground) Most likely
  2. Spark plug of cylinder 6 worn, sooted, cracked or wrongly gapped Most likely
  3. Injector of cylinder 6 clogged or leaking, or its control Possible
  4. Low compression on cylinder 6 (valve, rings, head gasket) or local false air Less likely
  5. Water or oil in the plug well Less likely

How to diagnose P0306

  1. Look up where cylinder 6 is on your engine. Depending on the maker it can be on either bank, at the front or the back, so use the numbering diagram for your exact engine.
  2. Before pulling the coil, look into the plug well for oil or coolant. Oil usually means a leaking seal that needs fixing too, or the misfire will come back.
  3. Swap the cylinder 6 coil with a neighboring one, clear the code and drive. If the misfire follows the coil, replace it.
  4. If a coil looks burned or melted, have the coil wiring checked. A wiring or control fault can damage coils, and the damaged coil isn't always the one on cylinder 6.
  5. If the spark plugs are due, replace the full set rather than just cylinder 6.
  6. If ignition parts are fine, have the cylinder 6 injector and compression tested.

Vehicles that report P0306 most

VehicleYearsReportsMedian miles
Honda Pilot2016–20198—
Jeep Wrangler2008–2018762k
Ford F-1502012–2016711k
Chrysler Pacifica2017–20195—
Toyota 4runner2004–20054133k
Honda Odyssey2013–20194—
Kia Sedona2016–20174—
Lincoln LS2003–2005330k
GMC Sierra 15002011–20203—
Dodge Grand Caravan2013–20173—

Counts of owner complaints to the NHTSA that mention P0306 (93 in total), not failure rates: popular models get more complaints simply because more of them are on the road. Models with fewer than 3 complaints are left out.

Reading the code

P
Powertrain
0
Generic (SAE) code
3
Ignition system or misfire
06
Specific fault

Questions drivers ask

Can I drive with code P0306?

Check the light first. If it's flashing, pull over and stop, because raw fuel is overheating the catalytic converter and can ruin it. If it's steady, drive gently and directly to a shop, and skip long trips until it's fixed.

Will my car pass an emissions inspection with P0306?

Probably not in states that test vehicles with an OBD-II scan: an emissions-related code that keeps the check engine light on is usually an automatic fail. Rules differ by state and county, so check yours.

Will P0306 clear by itself?

The light can go off after several drive cycles without the fault, but the code returns if the cause is still there. After a repair, the readiness monitors need a full drive cycle before an inspection.

Can I fix P0306 myself?

Often yes, with an OBD-II scanner and basic tools. Difficulty: easy. Start with the cheapest checks before replacing expensive parts.

Often reported together

Codes that owners mention in the same NHTSA complaints as P0306. They can point to a shared cause, so it's worth checking them together.

This page is general information, not a substitute for a professional diagnosis. Repair costs are rough estimates for parts and labor and vary by vehicle and region.