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. Step-by-step guide with diagnostic procedures and repair instructions.

Solution

1. Preparation

• Tools Required: OBD-II scanner, socket set, torque wrench, multimeter, compression tester, vacuum gauge.
• Ensure the vehicle is parked on a flat surface and the engine is cool. Disconnect the battery before beginning any work.

2. Replace Spark Plug

1. Remove the engine cover (if necessary) using a socket set.
2. Locate the spark plug for cylinder 4.
3. Use a spark plug socket to remove the old spark plug.
4. Inspect the spark plug for wear or damage. Replace it with a new spark plug that meets OEM specifications (typically, a heat range of 6 or 7).
5. Torque the new spark plug to the manufacturer’s specifications (usually around 22 lb-ft).
6. Reattach the ignition coil and any connectors.

3. Replace Ignition Coil

1. If misfire persists after replacing the spark plug, remove the ignition coil for cylinder 4.
2. Install a new ignition coil that is compatible with the Volkswagen Passat B8.
3. Reconnect all electrical connectors and ensure a secure fit.

4. Test Fuel Injector

1. Connect a fuel injector tester to the fuel injector for cylinder 4.
2. Activate the fuel injector to check for proper operation (listen for a clicking sound).
3. If the injector is faulty, replace it with a new one, ensuring the new injector is properly seated and connected.

5. Compression Test (if needed)

1. Remove the spark plug for cylinder 4.
2. Insert a compression tester into the spark plug hole.
3. Crank the engine and record the compression reading. Compare it with specifications (typically 150-200 psi).
4. If the compression is low, investigate further for valve, head gasket, or piston ring issues.