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How to Fix a P0303 Code – Causes, Symptoms and Cost

  • Cars Explained
  • Xavier Sabastian
  • 6 minutes

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How do I resolve error code P0303? It’s a straightforward question. Unfortunately, there may not be a straightforward remedy, as with many problem codes. We at Way.com appreciate the value of having a fully operating car, and we also realize how frustrating and stressful these little error codes can be. 

Cars today are extremely complex, relying heavily on a web of interconnected electronic systems to ensure proper operation. As a result, modern cars are as computer and data-driven as mechanical. Today’s cars can store one or more fault codes when a malfunction occurs. These trouble codes can be useful in determining the source of the problem and reducing vehicle downtime.

Let’s look at the P0303 error code and what it can signify for your car and your wallet.

Warning Light Neon GIF


P0303 Code Significance

“What does the code P0303 mean?” is probably the first question on your mind. Unfortunately, this is a typical error message on OBD-II enabled cars and pertains to powertrain difficulties. However, the Code does not always allude to specific measures that should be taken, as these will vary depending on your vehicle’s make and model. 

However, the Code indicates that the car’s computer system has detected a problem with at least one cylinder. The computer system in this situation of error code P0303 is informing the driver that cylinder number three is not firing properly.

P0303 Code Significance

What is the cause of the P0303 Code?

While it is usually preferable when the source of a problem is obvious and straightforward to repair, this error code can be caused by various variables ranging from inexpensive to costly. 

For example, the problem could be caused by a defective spark plug or wire, which is quite simple to fix in the great scheme of things. However, the error code could be caused by a damaged catalytic converter or computer system, which can be costly. 

There are, however, a variety of different options.

  • Coil failure
  • Fuel injector failure
  • Oxygen sensor failure Poor compression
  • Exhaust valve on the fire
  • Low or non-existent fuel

What to look out for in the P0303 Code?

While everything seems clearer now, it is still beneficial to be aware of the potential warning signals of this issue. For example, if your engine is more difficult to start, or if it stumbles or hesitates when turned on, it could be a sign that one of your cylinders isn’t working properly. 

However, locating the precise cylinder can be difficult without the help of the problem code message. So if you’re having trouble with your car but don’t see an error code, you should get it checked out.

How serious is the P0303 Code?

How serious is the P0303 Code?

Code P0303 is generally thought to be fairly severe. There are two main reasons for this generalization. First, a slew of driveability difficulties often accompanies code P0303, but an unresolved misfire can also lead to a slew of secondary issues over time.

Unburned fuel is sent downstream, through a car’s exhaust, when fuel is not combusted as intended, such as in a cylinder misfire. After that, the fuel is superheated, causing damage to many components, including the catalytic converter. A P0303 misfire code should be resolved as quickly as possible to reduce the danger of further damage. If you are unsure about diagnosing an issue on your own, take your vehicle to a reputable service center as soon as possible.

Diagnosis of P0303 Code

A mechanic can detect a cylinder three misfiring problem in a few different ways:

  • The mechanic can use their scan tool to examine the vehicle for any current, pending, or history codes.
  • They can then take that freeze frame data when they test drive the car.
  • The mechanic will next clear all of the codes from the OBD2 while driving the car to confirm any faults that could indicate a P0303 trouble code.
  • They should then conduct a thorough visual inspection to search for any broken components, wear and tear, leaks, and damaged wiring that could be the source of the problem or the code.
  • The mechanic will then use an OBD2 scan tool to verify the cylinder three misfire counter during operation.

Common Mistakes to Avoid

There will be an opportunity for error and blunders when diagnosing and correcting the cylinder three misfiring issues if these diagnosis stages are not followed properly. The most typical blunder is neglecting fuel or air intake leaks as the primary cause of the misfire. Even though spark plugs are the most typical source of this error code, they are not the primary cause of cylinder three misfirings.

Common Mistakes to Avoid

Fixing a P0303 Code

If you’re experiencing hesitancy or stumbling of the engine in addition to the error number, the issue is most likely with the spark plugs or wiring. 

Check that the connectors and wiring leading to the malfunctioning cylinder are secure and in excellent working order. However, replacing these ignition components as routine maintenance may be useful depending on the car’s age. It’s also possible that the catalytic converter has failed. 

If the exhaust smells like rotten eggs, you may be sure this is the case. It is advisable to analyze your skills before attempting any of these replacements because you do not want to cause any additional damage to your car. In certain cases, though, the computer has just failed and needs to be reset.

The P0303 OBD-II scanner error code can be aggravating. However, with time and the required expertise, you can find the source of the problem and restore your car to its full capacity.

Cost of repairing a car with Code P0303 issues

For $120, hire a licensed car mechanic to come to your home or workplace and perform a Check Engine Light diagnostic. These prices include components and labor and are based on national averages. Your pricing will vary depending on your location and vehicle type.

  • Spark plugs: $66-$250
  • Ignition Coils: $230-$640
  • Spark plug wires: $180-$240
  • Fuel injectors: $1500-$1900
  • Vacuum leak: $100-$200
  • Fuel pump: $1300-$1700
  • Fuel pressure regulator: $200-$400

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