P0303 Misfire in cylinder 3

Technical description of error P0303

DTC P0303 is set when the engine control unit (ECU, ECM or PCM) is having trouble starting cylinder 3.

What does this mean?

This Diagnostic Trouble Code (DTC) is a generic transmission code, which means it applies to OBD-II equipped vehicles. Although general, specific repair steps may differ depending on the brand / model.

The P0303 code means that the vehicle computer has detected that one of the engine cylinders is not working properly. In this case, this is cylinder # 3.

Symptoms of error P0303

The most common symptoms associated with this code are:

• Illumination of the Check Engine light on the dashboard. A general drop in engine performance, leading to a general malfunction of the vehicle. The engine stalls while driving or is difficult to start.

As you can see, these are fairly common symptoms that can be traced to other error codes as well.

Causes

DTC P0303 occurs when a malfunction causes ignition problems in cylinder 3. The engine control unit (ECU, ECM or PCM), detecting this malfunction, causes the automatic activation of error P0303. The most common causes of misfires in cylinders are the following:

• Spark plug failure caused by component wear or poor contact. Fuel injection error. Wiring and connection problems in general, which can also be attributed to a battery malfunction, which may not be sufficiently charged. Malfunction of the engine mechanical system affecting the cylinder ignition process. ignition coils. Insufficient cylinder compression 3. Intake air leaks. Faulty oxygen sensor. Faulty catalytic converter. Faulty engine control unit, issuing incorrect codes.

Possible Solutions to P0303

If there are no symptoms, the simplest thing is to reset the code and see if it comes back. If there are symptoms such as the engine stumbles or hesitates, check all wiring and connectors leading to the cylinders (such as spark plugs). Depending on how long ignition system components have been in the vehicle, it may be a good idea to replace them as part of a regular maintenance schedule. I would recommend spark plugs, spark plug wires, distributor cap and rotor (if applicable). Otherwise, check the coils (also known as coil packs). In some cases, the catalytic converter has failed. If you smell rotten eggs in your exhaust, your cat's transducer needs to be replaced. I have also heard that in other cases the problem has been faulty fuel injectors.

Additionally

P0300 - Random/Multiple Cylinder Misfire Detected

Repair Tips

After the vehicle is taken to the workshop, the mechanic will usually perform the following steps to properly diagnose the problem:

• Scan for error codes with an appropriate OBC-II scanner. Once this is done and after the codes have been reset, we will continue to test drive on the road to see if the codes reappear. Visual inspection of the electrical wiring for broken or broken wires and any shorts that may have affected electrical system Visual inspection of the cylinders, for example for worn components. intake air with a suitable instrument.

It is not recommended to proceed with the replacement of any component until all the above checks have been completed. While the most common cause of this DTC is actually a faulty spark plug, an air leak as well as an issue with the fuel injection system can also be the cause of this DTC. In general terms, the repair that most often clears this code is as follows:

• Replacing the spark plug in the cylinder. Replacing the spark plug cap. Replacing damaged cables. Eliminating air leaks. Repairing the fuel injection system. Repairing any mechanical problems with the engine.

Although it is possible to drive a car with this error code, it is recommended to deal with this problem in advance in order to also avoid more serious malfunctions that can seriously damage the engine. Also, given the complexity of the inspections, the DIY option in the home garage is definitely not feasible. It is difficult to estimate the upcoming costs, since a lot depends on the results of the diagnostics carried out by the mechanic. As a rule, the cost of replacing spark plugs in a workshop is about 60 euros.

Frequently Asked Questions (FAQ)

What does code P0303 mean?

DTC P0303 indicates trouble starting cylinder 3.

What causes the P0303 code?

The most common cause for this code to activate is faulty spark plugs, as they are worn out or clogged with grease or dirt buildup.

How to fix code P0303?

The wiring harness and spark plugs should be inspected first, replacing any faulty components and cleaning the area with a suitable cleaner.

Can code P0303 go away on its own?

Unfortunately, this error code does not go away on its own.

Can I drive with code P0303?

Driving a car on the road, while possible, is not recommended if this error code is present. In the long run, much more serious problems may arise.

How much does it cost to fix code P0303?

On average, the cost of replacing spark plugs in a workshop is about 60 euros.

Engine Misfire? Trouble Code P0303 Meaning, Diagnose Spark Plugs & Ignition Coils

Need more help with the P0303 code?

If you still need help with DTC P0303, post a question in the comments below this article.

NOTE. This information is provided for informational purposes only. It is not intended to be used as a repair recommendation and we are not responsible for any action you take on any vehicle. All information on this site is protected by copyright.