P0303

Cylinder 3 Misfire Detected

Severity: moderate Driveability: Safe To Drive AI generated

Plain-English meaning

The engine control module (ECM) has detected that cylinder number 3 is misfiring, meaning it is not firing properly or at the correct time.

What to check first

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What not to replace yet

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Stop driving when

If the engine runs very rough, stalls frequently, or if there is a noticeable loss of power that affects safe driving, it is advisable to stop driving and have the vehicle inspected promptly.

Related symptoms

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Owner steps

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Likely causes

Faulty spark plug in cylinder 3 (medium)

Defective ignition coil or ignition wire for cylinder 3 (medium)

Fuel injector malfunction or clog in cylinder 3 (medium)

Vacuum leak near cylinder 3 (medium)

Low compression in cylinder 3 due to mechanical issues (medium)

Wiring problems or poor electrical connections to cylinder 3 components (medium)

Faulty ECM or sensor inputs related to cylinder 3 (medium)

Shop steps

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Follow-up questions

Has the vehicle exhibited any recent changes in performance or fuel economy?

When was the last time the spark plugs and ignition components were serviced?

Are there any other diagnostic trouble codes present?

Has the vehicle experienced any recent repairs or incidents?

Is there any unusual noise or vibration from the engine?