how to fix P0302 misfire code on my BMW 3 Series E90/E91 (2005-2012)

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Disconnect the battery to prevent electrical shorts.
• Allow the engine to cool down completely before starting work.

2. Inspect and Replace Spark Plug

• Tools Required: Spark plug socket, ratchet, torque wrench
• Remove the ignition coil from cylinder 2 by unscrewing the retaining bolt and pulling it out.
• Remove the spark plug using the spark plug socket.
• Inspect the spark plug for wear or damage; replace it if necessary.
• Install the new spark plug and torque it to the manufacturer’s specifications (typically around 20 Nm).
• Reinstall the ignition coil.

3. Check and Replace Ignition Coil

• If the spark plug appears fine, test the ignition coil for proper operation using a multimeter.
• If defective, remove the ignition coil from cylinder 2.
• Install a new ignition coil, ensuring it is seated properly.
• Reconnect the electrical connector and secure it with the retaining bolt.

4. Inspect and Replace Fuel Injector

• If the problem persists, check the fuel injector for cylinder 2.
• Disconnect the fuel injector connector and remove the fuel rail if necessary.
• Use a fuel injector cleaner or replace the injector if clogged or defective.
• Reinstall the fuel rail and reconnect the injector connector.

5. Final Checks

• Reconnect the battery.
• Start the engine and check for any error codes using the OBD-II scanner.
• Monitor the engine to ensure the P0302 code does not return.