my BMW 3 Series F30/F31 (2012-2019) has a check engine light with code P0301

Solution

1. Preparation

• Gather tools and parts.
• Disconnect the negative battery terminal to prevent electrical issues.
• Allow the engine to cool before starting work.

2. Replace Spark Plug and Ignition Coil

• Tools Required: Socket set, torque wrench, dielectric grease.
• Sub-steps:
  1. Remove the engine cover (if applicable) by unscrewing any retaining bolts.
  2. Disconnect the ignition coil connector for cylinder 1.
  3. Remove the ignition coil by pulling it out of the spark plug hole.
  4. Use a spark plug socket to remove the spark plug.
  5. Inspect the old spark plug for damage or fouling.
  6. Install the new spark plug by hand to avoid cross-threading, then torque to manufacturer specifications (usually around 22 ft-lbs).
  7. Apply a small amount of dielectric grease to the ignition coil boot.
  8. Reinstall the ignition coil and reconnect the ignition coil connector.

3. Test Fuel Injector

• Tools Required: Noid light, multimeter.
• Sub-steps:
  1. Disconnect the fuel injector connector for cylinder 1.
  2. Connect the Noid light to the injector connector and crank the engine.
  3. If the Noid light does not flash, check the wiring and ECM output.
  4. If the injector is faulty, replace it with a new unit.

4. Perform Compression Test (if necessary)

• Tools Required: Compression tester.
• Sub-steps:
  1. Remove the spark plug for 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.
  4. Compare the reading to manufacturer specifications. If low, further diagnostics may be needed for internal engine issues.