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

Solution

1. Preparation

• Gather tools: OBD-II scanner, socket set, torque wrench, multimeter, compression tester, and replacement parts.
• Disconnect the battery to ensure safety.

2. Replace Spark Plug

• Sub-steps:
  1. Remove the engine cover (if applicable) using the socket set.
  2. Locate the spark plug for cylinder 1.
  3. Using the spark plug socket, remove the old spark plug.
  4. Check the spark plug gap and install a new spark plug, ensuring it is properly gapped as per manufacturer specifications.
  5. Torque the new spark plug to the manufacturer's specifications (usually around 20 Nm).

3. Replace Ignition Coil

• Sub-steps:
  1. Unplug the electrical connector from the ignition coil.
  2. Remove the ignition coil bolt using the socket set.
  3. Pull the ignition coil out of the cylinder head.
  4. Install the new ignition coil and secure it with the bolt. Torque the bolt to the specified value.
  5. Reconnect the electrical connector.

4. Test Fuel Injector

• Sub-steps:
  1. Disconnect the fuel injector connector from cylinder 1.
  2. Using a multimeter, check the injector resistance (typically around 12-16 ohms).
  3. If the injector is faulty, replace it by removing the injector retaining clips and pulling it out.
  4. Install the new injector and reconnect the connector.

5. Perform a Compression Test

• Sub-steps:
  1. Remove the spark plug from cylinder 1.
  2. Insert the compression tester into the spark plug hole.
  3. Crank the engine for a few seconds and record the compression reading. It should be within the manufacturer's specifications.
  4. If the reading is low, investigate potential internal engine issues.