how to diagnose P0301 misfire code in BMW 3 Series F30/F31 (2012-2019)

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Ensure the vehicle is on a level surface and the engine is off.
• Disconnect the negative battery terminal to prevent any electrical issues.

2. Inspect and Replace Spark Plug

• Remove the ignition coil cover if applicable.
• Use a socket wrench to remove the spark plug from cylinder 1.
• Inspect the spark plug for signs of wear, carbon buildup, or damage.
• If the spark plug is worn, replace it with a new one, ensuring it meets OEM specifications (typically NGK or Bosch).
• Torque the spark plug to the manufacturer’s specification (usually around 20 Nm).

3. Check and Replace Ignition Coil

• Remove the ignition coil from cylinder 1.
• If swapping it with another cylinder, reinstall the coil from that cylinder and test for misfire codes again.
• If the misfire follows the ignition coil, replace it with a new OEM part.
• Ensure proper seating and secure with the appropriate torque.

4. Test Fuel Injector

• Disconnect the injector connector for cylinder 1.
• Use a noid light to check for injector pulse; it should flash when the engine is cranked.
• If there is no pulse, inspect the wiring and connectors for damage.
• If the injector is faulty, replace it with a new one, ensuring to clean any debris before installation.

5. Compression Test

• Remove the spark plug for cylinder 1 and insert the compression tester.
• Crank the engine and record the compression reading. Compare it to OEM specifications (typically around 160-200 psi).
• If the compression is low, further diagnostics are needed to check for internal engine problems.