Worn, fouled or incorrectly gapped spark plug on cylinder 6; Faulty ignition coil or coil connector on cylinder 6; Faulty or blocked fuel injector on cylinder 6, or a wiring fault to it; Vacuum or intake air leak affecting cylinder 6, such as a split manifold gasket or seal; Low compression on cylinder 6 from a burnt valve, worn rings or head gasket leak; Wiring or connector damage in the ignition or injector circuit for cylinder 6; Valve train fault such as a worn camshaft lobe or a sticking lifter, depending on engine.

P0306

Cylinder 6 Misfire Detected.

Generic
Powertrain
Generic code
High severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
3: AreaIgnition system or misfire
06: FaultThe specific fault in that area

What it means

P0306 means the engine control unit has detected a misfire on cylinder 6, using crankshaft speed variation to spot the cylinder not contributing its share of power. The count of misfire events passed the calibrated threshold, either at emissions-damaging levels or high enough to risk catalyst damage. The code can only set on engines with six or more cylinders, and cylinder numbering depends on the engine layout.

Symptoms

Rough running or noticeable shaking at idle
Flashing or steady engine warning light
Hesitation, jerking or loss of power under acceleration
Smell of unburnt fuel from the exhaust
Higher fuel consumption
Difficulty starting or occasional stalling

Possible causes

Worn, fouled or incorrectly gapped spark plug on cylinder 6likely
Faulty ignition coil or coil connector on cylinder 6likely
Faulty or blocked fuel injector on cylinder 6, or a wiring fault to itpossible
Vacuum or intake air leak affecting cylinder 6, such as a split manifold gasket or sealpossible
Low compression on cylinder 6 from a burnt valve, worn rings or head gasket leakrare
Wiring or connector damage in the ignition or injector circuit for cylinder 6possible
Valve train fault such as a worn camshaft lobe or a sticking lifter, depending on enginerare

How to diagnose

Read the freeze frame data and note load, engine speed, temperature and whether other misfire codes are stored
Check live misfire counters to confirm whether the misfire is confined to cylinder 6 and when it occurs
Inspect the coil, plug lead if fitted, and connectors on cylinder 6 for damage, moisture, oil or corrosion
Remove the cylinder 6 spark plug and check its condition and gap against the manufacturer's specification
Swap the cylinder 6 coil with another cylinder, clear the code and see whether the misfire follows the coil
Test the cylinder 6 injector's resistance and operation, and check its wiring and driver signal
Smoke test or inspect the intake system for leaks near cylinder 6
Carry out a compression or leak-down test on cylinder 6 if ignition and fuel checks are clear

How to fix

Replace the spark plugs as a set to the specified type and gap
Replace the faulty ignition coil
Clean or replace the faulty injector, or repair its wiring
Repair intake leaks by replacing the faulty gasket, seal or hose
Repair damaged wiring or connectors in the affected circuit
Carry out the necessary engine repair if the compression test shows mechanical damage

Can I keep driving?

High severity

Avoid driving if the warning light is flashing, as unburnt fuel can overheat and damage the catalytic converter. If the misfire is mild and the light is steady, drive gently and only as far as needed to get it repaired promptly.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.