StopOrDrive

Enter a 5-character code such as P0420, P0301, or P0457.

We don't have that code yet

Codes starting with P are engine and transmission, B are body, C are chassis, and U are network communication. A 0 as the second character means a generic code shared by all makes; a 1 means a manufacturer-specific code, so its meaning depends on your brand.

A steady check engine light usually means get it checked soon. A flashing check engine light means an active misfire: reduce speed and stop driving as soon as it is safe.

That doesn't look like an OBD-II code

A valid code is one letter (P, B, C, or U) followed by four characters, for example P0420.

P0303 Cylinder 3 misfire detected

Can I drive with P0303?

Drive soon

OK to drive for now, but get it fixed within days to a couple of weeks, or the damage and the bill can grow.

With a steady light, drive gently and get it checked soon. Misfires waste fuel and slowly damage the catalytic converter.

If your check engine light is flashing, treat this as Stop now: an active misfire dumps unburned fuel into the exhaust and can destroy the catalytic converter within miles.

What does P0303 mean?

Cylinder 3 is not burning its fuel properly, so the engine computer detected that cylinder stumbling. You may feel shaking at idle or a loss of power.

What causes P0303?

  1. Worn spark plug in cylinder 3
  2. Faulty ignition coil on cylinder 3
  3. Clogged or failed fuel injector for cylinder 3
  4. Vacuum leak near that cylinder
  5. Low compression from a valve or head gasket problem

How much does it cost to fix P0303?

$100 – $600

Spark plugs: $100–$300 at a shop. Ignition coil: $150–$400. Fuel injector: $250–$600. Compression problems cost $1,000 or more.

Confirm the code yourself

A low-cost scanner lets you read the code, clear it, and see if it comes back before paying for a diagnosis.

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