Description of DTC code P0303

This DTC code P0303 informs us that the vehicle´s computer ECM (Engine Control module) has detected that one of the engine´s cylinders is not firing properly. And the fault for this DTC code P0303 corresponds to cylinder number 3 of the engine.

Symptoms of fault code P0303

  • When starting the engine, you may have difficulty or you may trip.
  • Unstable motor
  • There are problems when starting the vehicle, it may ignite after several unsuccessful attempts
  • The engine manages to turn on, but does not stay on for a sufficient time.


Causes of OBD2 P0303

A P0303 code can have one or more of the following problems:


  • Spark plug or wire damage.
  • Some of the oxygen sensors are failing.
  • The fuel injector may be failing.
  • The exhaust valve is burned.
  • The catalytic converter is defective.
  • The fuel tank is empty or dirty.
  • Compression of the gas pump is poor.
  • The PCM (Powertrain Control Module) computer may be damaged or the cables may be damaged.

Possible solutions of the DTC code P0303

To fix the DTC code P0303 you can check the following components:

  • Check the wires and spark plugs.
  • Carry out maintenance on the spark plugs and check that they are not worn or full of coal, gasoline or oil.
  • Check the coil and that its cables are passing enough current
  • Examine the fuel injectors one by one and proceed to maintain them. Additionally, verify that the injectors do not leak gasoline.
  • Check the Mass Air Flow Sensor, especially if it is not dirty with oil or water.
  • Check the Mass Air Flow Sensor that when the engine accelerates, the signal goes up and decreases when decelerating it.
  • Check the EGR valve (Exhaust Gas Recirculation), as it can be open or short.

Codes related to P0303

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