P0303 - Cylinder 3 Misfire Detected

The OBD-II code P0303 indicates a "Cylinder 3 Misfire Detected" in the engine. This code is triggered when the engine control module (ECM) detects a misfire in the combustion process of Cylinder 3.

A misfire in Cylinder 3 occurs when the air-fuel mixture in the combustion chamber fails to ignite properly, leading to incomplete combustion in that specific cylinder. Similar to other misfire codes, P0303 can be caused by various factors, including:

1. Ignition system problems: A faulty spark plug, ignition coil, or spark plug wire for Cylinder 3 can lead to misfires.

2. Fuel system issues: A clogged or malfunctioning fuel injector for Cylinder 3 can disrupt the proper fuel delivery.

3. Compression problems: Low compression in Cylinder 3 due to issues like a damaged piston, worn piston rings, or a blown head gasket can cause misfires.

4. Air intake problems: A vacuum leak in the intake manifold or a faulty airflow sensor can affect the air-fuel mixture.

To diagnose and resolve the P0303 code, you can follow these steps:

1. Inspect the ignition system: Check the spark plug, ignition coil, and spark plug wire for Cylinder 3. If any of these components are faulty, replace them.

2. Check the fuel injector: Ensure that the fuel injector for Cylinder 3 is functioning correctly. It may need cleaning or replacement if it's clogged or malfunctioning.

3. Check engine compression: Perform a compression test for Cylinder 3 to check for any compression issues. If the compression is low, further diagnosis is required to identify the root cause.

4. Inspect the air intake system: Check for vacuum leaks in the intake manifold and ensure that the airflow sensor is working properly.

5. Reset the ECM: After making any necessary repairs or replacements, reset the ECM using a scan tool.

After addressing the identified issue, test-drive the vehicle and monitor the system to see if the P0303 code reappears. If the code persists, it's recommended to have the vehicle inspected by a qualified mechanic or dealership. Advanced diagnostics may be needed to pinpoint the exact cause of the Cylinder 3 misfire and implement the appropriate repairs.