how to diagnose P0305 misfire code on my Volkswagen Passat B8 (2015-2022)

Solution

1. Preparation

• Tools Required: OBD-II scanner, socket set, torque wrench, compression tester, multimeter.
• Disconnect the vehicle battery to ensure safety while working on electrical components.

2. Inspect and Replace Spark Plug

• Remove the engine cover if applicable.
• Disconnect the ignition coil connector from cylinder 5.
• Remove the ignition coil bolt and carefully pull the coil out.
• Remove the spark plug using a spark plug socket.
• Inspect the spark plug for wear or damage; replace if necessary.
• Install a new spark plug, torque to 30 Nm (22 lb-ft).
• Reinstall the ignition coil and reconnect the connector.

3. Inspect and Replace Ignition Coil

• If the ignition coil shows signs of failure, replace it.
• Remove the faulty ignition coil and install a new one.
• Make sure to torque the coil mounting bolt to the manufacturer's specification.
• Reconnect the ignition coil connector.

4. Perform Compression Test

• Remove the spark plug from cylinder 5.
• Insert the compression tester into the spark plug hole.
• Crank the engine for a few seconds to take the reading.
• Compare the reading to the manufacturer's specifications (should be around 150 psi or as specified).
• If low, further investigation into the engine's mechanical condition is needed.

5. Inspect Fuel Injector

• Check the electrical connector for the fuel injector on cylinder 5 for proper voltage using a multimeter.
• If the injector is faulty, replace it by removing the fuel rail and replacing the injector with a new one.
• Reassemble the fuel system and ensure no leaks occur.