What Does the Engine Code P0303 Mean?

If your car displays the engine code P0303, your engine’s cylinder three is misfiring incorrectly and could pose a severe safety risk.
Written by Kevin Martinez
Reviewed by Melanie Reiff
If your car displays the engine code P0303, that might mean you are having issues with your engine’s cylinder 3. You must get it checked and resolved promptly, or it could lead to engine damage and pose a high safety risk when driving.
Your car is equipped with technology that can communicate when it has an issue known as diagnostic trouble codes (DTCs). These DTCs, which can be read using an OBD-II reader, can help diagnose any problems your car may be having. 
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What does the engine code P0303 mean?

Definition: Cylinder 3 misfire detected
The P0303 engine code usually indicates that your engine third cylinder is experiencing a misfire. This means that your cylinder is not correctly burning the right amount of fuel within the cylinder. It’s an important issue since your cylinder provides the adequate energy needed to start your engine.

How much will it cost to fix?

Although it can vary depending on your car’s make and engine type, mechanics typically charge anywhere from $75-$150 per hour of labor and parts needed. 
The final cost will ultimately depend on what the mechanic needs to fix. This may include the following:

What can cause the P0303 code?

If you see the P0303 engine code, chances are you may be having trouble with your engine’s cylinder number 3 not burning fuel adequately. Common factors that can cause the code to appear to include:
  • Intake air leak
  • Faulty spark plugs
  • Incorrect fuel pressure
  • Clogged or faulty fuel injector
The engine control module (ECM) in your vehicle will determine a misfire in your cylinders by using the
crankshaft position sensor
. Based on the various speeds of the crankshaft position, the ECM will determine if there is a misfire within the cylinder, and thus the code will appear.

Common symptoms of P0303 engine code

One of the leading indicators for a P0303 engine code issue is your car’s service engine light. It’s crucial that you get your car in for service as soon as possible to avoid further damage to the engine.
Here are some other common symptoms that are usually correlated to a P0303 engine code:

How serious is the P0303 engine code?

If not addressed promptly, this issue could cause further damage to both the catalytic converter and issues with the ignition. You must get it checked as soon as you notice the problem, as it could pose a severe driving hazard risk and cause further (expensive) damage to your engine.

Can I fix the P0303 engine code myself?

While attempting to resolve the issue by yourself might be the most affordable option, it’s always best to have a mechanic or licensed repairman properly diagnose the issue. 
If you have car experience and want to check things out yourself, here’s what you can look for:
  • Visible signs of damage, such as damaged wiring or connector pins
  • Signs of intake leaks
  • Spark plugs that need to be replaced or repaired
If these don’t indicate any issues, a mechanic will need to run additional tests to determine what’s happening.

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