how to fix P0304 code in Volkswagen Passat B8 (2015-2022)

Learn how to diagnose and fix P0304 cylinder 4 misfire in Volkswagen Passat B8 (2015-2022). Step-by-step guide with diagnostic procedures and repair instructions.

Solution

1. Preparation

• Gather tools and parts.
• Disconnect the battery to ensure safety while working on the electrical components.
• Allow the engine to cool down before starting work.

2. Replace Spark Plug

• Tools Required: Socket set, torque wrench, spark plug socket.
• Remove the engine cover (if applicable) by unscrewing the retaining bolts.
• Disconnect the ignition coil connector for cylinder 4.
• Unscrew and remove the ignition coil.
• Remove the old spark plug using a spark plug socket.
• Install a new spark plug, ensuring it is gapped correctly to the manufacturer's specifications (typically 0.028 inches for a VW).
• Torque the spark plug to the manufacturer's specifications (usually around 20 Nm).
• Reinstall the ignition coil, ensuring it clicks into place, and reconnect the connector.

3. Replace Ignition Coil (if necessary)

• Tools Required: Socket set, torque wrench.
• If the ignition coil was found faulty during diagnostics, remove it as described above.
• Install the new ignition coil, ensuring it is seated properly.
• Torque the ignition coil bolts to the manufacturer's specifications (typically around 10 Nm).
• Reconnect the ignition coil connector.

4. Inspect and Clean Fuel Injector (if necessary)

• Tools Required: Fuel injector cleaning kit (if cleaning), or new fuel injector.
• If the fuel injector is suspected to be faulty, remove it following the manufacturer's service manual.
• Clean the fuel injector with a suitable cleaner or replace it if necessary.
• Reinstall the fuel injector and reconnect any associated connectors.

5. Reconnect Battery and Test

• Reconnect the battery terminals.
• Start the engine and check for any warning lights.
• Allow the engine to idle and check for smooth operation.