Share a caseSign in
IgnitionSeverity High: diagnose before driving on

P0303Cylinder 3 Misfire Detected

What it means

The ECU has seen cylinder 3 misfire: the crankshaft slows down each time that cylinder should fire. A misfire that is bad enough to flash the check engine light can overheat and damage the catalytic converter.

Symptoms

  • Engine shakes or runs rough
  • Loss of power, especially under load
  • Flashing check engine light under load

Common causes

  • Ignition coil or spark plug on cylinder 3
  • Injector on cylinder 3 (clogged, leaking or not firing)
  • Low compression on cylinder 3
  • Vacuum leak close to that cylinder

What to check first

  1. Swap the coil (and plug) with another cylinder and see whether the misfire follows
  2. Check the injector (resistance, scope, balance test)
  3. Run a compression test on that cylinder
Can I drive with P0303? Not recommended. P0303 can lead to stalling, limp mode or engine damage; diagnose it before driving further.
Practise it: Ignition coil, cyl. 3 in the engine simulator shows this fault in live data, tests and on the scope.Open in the simulator

Generic OBD-II meaning. Manufacturer-specific meanings and checks can differ; always check the service information for the car.

How to test the parts behind P0303

Ignition coil (coil-on-plug)Wiring, typical values, multimeter and scope tests

Known engine problems that set P0303

1.2/1.4 TSI EA111: Cracked pistons on the high-output 1.4 TSIVolkswagen, Audi, Skoda, Seat · typically 80,000–180,000 km1.8/2.0 TFSI EA888: High oil consumption (piston rings)Audi, Volkswagen, Skoda, Seat · typically 60,000–160,000 km1.8/2.0 TFSI EA888: Carbon build-up on the intake valvesAudi, Volkswagen, Skoda, Seat · typically 80,000–160,000 km1.2 PureTech: High oil consumptionPeugeot, Citroën, DS, Opel · typically 60,000–160,000 km1.6 THP/Prince: Oil consumption and carbon build-upMini, BMW, Peugeot, Citroën, DS · typically 60,000–160,000 km1.2 TCe: High oil consumptionRenault, Dacia, Nissan, Mercedes-Benz · typically 40,000–120,000 kmTheta II 2.0/2.4: Carbon build-up on the intake valves (GDI)Hyundai, Kia · typically 80,000–180,000 kmMultiAir/TwinAir: MultiAir actuator failureFiat, Alfa Romeo, Lancia · typically 80,000–180,000 km1.6 GDI Gamma: Carbon build-up on the intake valvesHyundai, Kia · typically 80,000–160,000 km1.8 Hybrid 2ZR-FXE: Clogged EGR system, misfire and head gasket damageToyota, Lexus · typically 150,000–300,000 km

Cases with P0303 (0)

Share yours

No published cases with this code yet.

Colleagues asking about P0303

Ask for help

Stuck on P0303? Describe what you measured and ask the community.

P0303: questions and answers

What does P0303 mean?

P0303: Cylinder 3 Misfire Detected. The ECU has seen cylinder 3 misfire: the crankshaft slows down each time that cylinder should fire. A misfire that is bad enough to flash the check engine light can overheat and damage the catalytic converter.

What are the symptoms of P0303?

Engine shakes or runs rough. Loss of power, especially under load. Flashing check engine light under load.

What causes P0303?

Ignition coil or spark plug on cylinder 3. Injector on cylinder 3 (clogged, leaking or not firing). Low compression on cylinder 3. Vacuum leak close to that cylinder.

How do you diagnose P0303?

1. Swap the coil (and plug) with another cylinder and see whether the misfire follows 2. Check the injector (resistance, scope, balance test) 3. Run a compression test on that cylinder

Can I drive with P0303?

Not recommended. P0303 can lead to stalling, limp mode or engine damage; diagnose it before driving further.