how can I fix misfire code P0301 in my BMW 3 Series G20/G21 (2019-2024)

Solution

1. Preparation

• Gather tools and equipment: OBD-II scanner, socket set, torque wrench, multimeter, compression tester, and a fuel injector cleaning kit.
• Disconnect the negative battery terminal to ensure safety while working on electrical components.

2. Inspect and Replace Spark Plug

• Remove Engine Cover: Use a socket set to remove any bolts securing the engine cover; lift and set it aside.
• Remove Spark Plug:
  • Disconnect the ignition coil connector.
  • Remove the ignition coil using a socket wrench.
  • Use a spark plug socket to remove the spark plug from cylinder 1.
• Inspect Spark Plug: Check for signs of wear or carbon buildup. Replace with a new spark plug if necessary (specify gap as per manufacturer’s specs).
• Reinstall Spark Plug and Coil: Torque the spark plug to manufacturer specifications (generally around 20 Nm). Reinstall the ignition coil and reconnect its connector.

3. Inspect and Replace Ignition Coil

• If the spark plug is in good condition, proceed to inspect the ignition coil.
• Remove Ignition Coil: Follow the same steps to remove the ignition coil from cylinder 1.
• Test Ignition Coil: Use a multimeter to check the resistance; replace if it is out of specifications.
• Install New Ignition Coil: Secure the new ignition coil and reconnect the electrical connector.

4. Fuel Injector Cleaning/Replacement

• If misfire persists, inspect the fuel injector for cylinder 1.
• Access Fuel Injector: Remove any necessary components to gain access to the fuel rail.
• Test Fuel Injector: Use a multimeter to check resistance and ensure proper function.
• Clean or Replace Injector: If the injector is clogged, clean it using a fuel injector cleaning kit. If it fails the resistance test, replace it with a new one.

5. Compression Test (if necessary)

• If no issues found with spark plug or ignition coil, perform a compression test on cylinder 1.
• Insert Compression Tester: Remove the spark plug and screw in the compression tester.
• Crank Engine: Crank the engine for a few seconds and note the compression reading.
• If compression is low, further engine diagnostics may be required to check for internal issues (e.g., valves, piston rings).