HomeTrouble CodesP0306

P0306 — Cylinder 6 Misfire Detected

Generic OBD-II · all makesPowertrain (engine & transmission)

This code indicates the engine control module has detected a combustion misfire specifically in cylinder 6. Continued driving with this condition can lead to catalytic converter damage and reduced engine performance. The issue is typically isolated to ignition, fuel, or mechanical components within that specific cylinder.

Symptoms

What causes it — most likely first

1. Ignition system failure

Worn spark plugs or failed ignition coils are the most frequent cause of isolated cylinder misfires.

2. Fuel injector malfunction

A clogged or electrically faulty fuel injector can prevent the correct amount of fuel from entering the cylinder.

3. Intake vacuum leak

An air leak at the intake manifold gasket near cylinder 6 can lean out the air-fuel mixture.

4. Low engine compression

Worn piston rings or burned valves may result in insufficient compression to ignite the mixture.

5. Wiring harness or connector damage

Damaged wiring or corroded connectors at the coil or injector can interrupt electrical signals.

6. Faulty engine control module (PCM)

Internal failure of the PCM is statistically improbable and should only be considered after all other circuits are tested.

How it's diagnosed

  1. Visually inspect the spark plug and ignition coil on cylinder 6 for cracks, wear, or carbon tracking.
  2. Swap the ignition coil with another cylinder to see if the misfire code follows the component.
  3. Listen to the fuel injector with a mechanic's stethoscope or test electrical pulse with a noid light.
  4. Conduct a compression test on cylinder 6 to rule out internal mechanical engine damage.
  5. Check wiring harnesses and connectors for continuity, corrosion, or physical damage.
  6. Measure voltage and ground signals at the PCM connectors before suspecting module failure.

Code facts & related codes

SystemPowertrain (engine & transmission)
StandardizationSAE generic — identical on every make

Frequently asked

Can I continue driving with this code?

Driving should be minimized, as a flashing light indicates catalyst-damaging misfires that require immediate attention.

Do I need to replace the engine computer?

No, PCM failure is extremely rare for this code; focus on ignition, fuel, and mechanical components first.

Will resetting the light fix the problem?

No, resetting clears the memory temporarily but the code will return until the underlying fault is repaired.

Why is only cylinder 6 affected?

The monitoring system isolates misfires to specific cylinders based on crankshaft rotation data to aid diagnosis.