how to diagnose P0301 misfire code in my BMW 3 Series G20/G21 (2019-2024)

Solution

1. Preparation

• Gather tools and necessary parts.
• Ensure the vehicle is parked on a level surface with the engine off and cool.
• Disconnect the negative terminal of the battery to prevent electrical shorts.

2. Spark Plug and Ignition Coil Replacement

• Remove Engine Cover: If applicable, remove any engine covers to access the ignition coils.
• Remove Spark Plug: Use a spark plug socket to carefully unscrew and remove the spark plug from cylinder 1. Inspect for wear or damage.
• Replace Spark Plug: Install a new spark plug, ensuring it is gapped correctly to manufacturer specifications. Torque to 18 Nm (13 lb-ft).
• Remove Ignition Coil: Unscrew the ignition coil retaining bolts and carefully pull it out. Inspect for signs of wear or damage.
• Replace Ignition Coil: Install a new ignition coil, ensuring it is seated properly. Torque retaining bolts to 10 Nm (7 lb-ft).

3. Fuel Injector Testing and Replacement

• Remove Fuel Injector Connector: Disconnect the electrical connector from the fuel injector for cylinder 1.
• Test Fuel Injector: Use a noid light to check for proper operation. If faulty, proceed to replace.
• Remove Fuel Injector: Use a fuel injector puller or suitable tool to remove the injector from its seat. Inspect O-rings for wear.
• Install New Fuel Injector: Lubricate new O-rings with engine oil and insert the new injector. Reconnect the electrical connector.

4. Reassembly and Final Checks

• Reinstall any components removed for access, including the engine cover.
• Reconnect the negative battery terminal.
• Clear any fault codes using the OBD-II scanner.