How do you fix fault code P0306?

STEP 1: Perform a 'Swap-test'. Move the ignition coil from cylinder 6 to a known good cylinder (e.g., cylinder 1). Clear the code and road test. If the code changes to P0301, the coil is faulty. STEP 2: Inspect the spark plug for fouling, fuel wetting, or cracked porcelain. Gap should be within OEM specs (typically 0.030-0.045 inches). STEP 3: Measure fuel injector resistance (typically 12-16 Ohms) and check for pulse using a Noid light or oscilloscope. STEP 4: Perform a dry and wet compression test. Expected values vary but should be within 10% of other cylinders. STEP 5: Check for vacuum leaks near the intake manifold runner for cylinder 6.

Powertrain (Engine & Gearbox)Standard EOBD

P0306 - Cylinder 6 - Misfire Detected

Q: What are the symptoms of fault code P0306?

• Check Engine Light (MIL) on or flashing • Rough idling and engine vibrations • Noticeable loss of engine power • Increased fuel consumption and raw fuel smell from exhaust • Hesitation or jerking during acceleration

Q: What causes fault code P0306?

• Most likely: Faulty ignition coil or spark plug on cylinder 6 • Likely: Fuel injector failure (clogged or electrical circuit fault) • Possible: Low cylinder compression (burned valve, worn rings, or head gasket leak) • Rare: Wiring harness issues (chafing, corrosion, or poor connection at ECU) • Rare: Mechanical valvetrain failure (camshaft lobe wear or lifter issue)

Last updated:1 February 2026

Related:Spark Plug, Ignition Coil, Fuel Injector, Crankshaft Position Sensor, ECU, Head Gasket

System

Powertrain (Engine & Gearbox)

Related Fault Codes

P0300

Random or Multiple Cylinder Misfire Detected

P0301

Cylinder 1 Misfire Detected

P0302

Cylinder 2 Misfire Detected

P0303

Cylinder 3 Misfire Detected

Technical Description

P0306 is an OBD-II diagnostic trouble code (DTC) indicating that the Engine Control Unit (ECU) has detected multiple misfire events on cylinder 6. The monitoring is performed by the Crankshaft Position (CKP) sensor measuring micro-fluctuations in crankshaft angular velocity. A lack of acceleration during the power stroke of cylinder 6 triggers the code. If the misfire rate is high enough to damage the catalytic converter, the Malfunction Indicator Lamp (MIL) will flash. This system affects the closed-loop fuel control and O2 sensor readings due to unburned oxygen entering the exhaust.

Possible Causes

Faulty ignition coil or spark plug on cylinder 6

Fuel injector failure (clogged or electrical circuit fault)

Low cylinder compression (burned valve, worn rings, or head gasket leak)

Wiring harness issues (chafing, corrosion, or poor connection at ECU)

Mechanical valvetrain failure (camshaft lobe wear or lifter issue)

Symptoms

Check Engine Light (MIL) on or flashing

Rough idling and engine vibrations

Noticeable loss of engine power

Increased fuel consumption and raw fuel smell from exhaust

Hesitation or jerking during acceleration

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Berörda ECU-familjer

SIEMENS / CONTINENTAL

MSD80

37 OEM

P0306 - Cylinder 6 - Misfire Detected

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Technical Description

Possible Causes

Symptoms

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Workflow

Mechanic's Tip

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other fault codes?

Berörda ECU-familjer

P0306 - Cylinder 6 - Misfire Detected

Related Fault Codes

Technical Description

Possible Causes

Symptoms

Recommended Solution

Workflow

Mechanic's Tip

Do you also have other fault codes?

Berörda ECU-familjer

Do you also have
other fault codes?