P0306Cylinder 6 Misfire Detected
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car 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.
- What you may notice
- Check engine light on, flashing at a catalyst-damaging rate
- Rough idle, jerking, vibration
- Loss of power, hesitation
- Smell of unburnt fuel, higher consumption
- Likely causes
- LikelyIgnition coil of cylinder 6 faulty (coil, connector, ground)
- LikelySpark plug of cylinder 6 worn, sooted, cracked or wrongly gapped
- PossibleInjector of cylinder 6 clogged or leaking, or its control
- RareLow compression on cylinder 6 (valve, rings, head gasket) or local false air
- RareWater or oil in the plug well
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Easy · Often possible to do yourself.Typical cost: €30 – €800
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.