DTC P0303 Cylinder 3 Misfire Detected

Your commitment to the well-being of your vehicle is truly impressive, and your extensive knowledge of potential issues is crucial for maintaining its optimal performance. DTC P0303, related to a “Cylinder 3 Misfire Detected,” is a concern that can disrupt the smooth operation of your engine. In this comprehensive guide, we will delve into the causes, symptoms, inspection methods, resolutions, and the process of clearing DTC P0303. With this knowledge, you can confidently address the issue and ensure your engine’s efficiency.

1. Causes of DTC P0303:

DTC P0303 is triggered when the engine control module detects a misfire specifically occurring in Cylinder 3. There are several factors that could contribute to this issue:

  • Ignition System Issues: A malfunctioning spark plug, ignition coil, or spark plug wire in Cylinder 3 can lead to misfires.
  • Fuel Delivery Problems: Inadequate fuel supply, a clogged fuel injector, or a faulty fuel pressure regulator can cause misfires.
  • Air-Fuel Mixture Imbalance: An improper balance of air and fuel entering Cylinder 3 can result in misfires.
  • Compression Irregularities: Problems with valves, piston rings, or other internal components can cause Cylinder 3 misfires.

2. Symptoms of DTC P0303:

Being observant of potential symptoms can help you identify the issue promptly:

  • Engine Vibrations: You might experience vibrations or shaking in the engine, particularly when Cylinder 3 is affected.
  • Power Loss: Your vehicle’s power and acceleration could decrease due to misfires in Cylinder 3.
  • Check Engine Light: The check engine light may illuminate, indicating a misfire-related problem.

3. Inspection of DTC P0303:

A thorough inspection is vital for accurately diagnosing the Cylinder 3 misfire issue:

  • OBD-II Scanner: Use an OBD-II scanner to confirm that the misfire is specific to Cylinder 3.
  • Inspect Ignition Components: Examine the spark plug, ignition coil, and spark plug wire in Cylinder 3 for wear or damage.
  • Evaluate Fuel System: Check Cylinder 3’s fuel injector, fuel pressure, and fuel filter for proper operation.
  • Air Intake Assessment: Look for vacuum leaks or air intake problems affecting Cylinder 3’s air-fuel mixture.
  • Compression Test: Perform a compression test on Cylinder 3 to assess its internal health.

4. Resolving Causes of DTC P0303:

Based on your inspection, take these steps to address the Cylinder 3 misfire issue:

  • Replace Faulty Components: If necessary, replace damaged spark plugs, ignition coils, or other ignition components in Cylinder 3.
  • Clean or Replace Fuel Injector: Clean a clogged fuel injector or replace a malfunctioning one in Cylinder 3 to ensure proper fuel delivery.
  • Address Air Intake Issues: Rectify vacuum leaks or air intake problems affecting Cylinder 3’s air-fuel mixture.
  • Engine Repairs: If internal problems in Cylinder 3 are identified, like low compression, take appropriate action to resolve them.

5. Clearing DTC P0303:

After addressing the root cause of the misfire, clear the code and reset the check engine light:

  • OBD-II Scanner: Utilize an OBD-II scanner to clear the code and turn off the check engine light.
  • Test Drive: Take the vehicle for a test drive to confirm resolution and ensure the light remains off.


Your dedication to resolving issues like DTC P0303 reflects your commitment to maintaining your vehicle’s performance. Being informed about potential problems contributes to the longevity and efficiency of your vehicle. Responsible car ownership entails both enjoying the driving experience and ensuring the health of your engine’s components. This guide serves as your companion throughout your journey as a car owner, even when addressing specific cylinder misfires like Cylinder 3, to ensure your engine operates at its best.