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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to prevent electrical shorts.
• Allow the engine to cool if it has been running.

2. Inspect and Replace Spark Plug

• Tools Required: Socket set, torque wrench.
• Remove the ignition coil from cylinder 1 by unscrewing the retaining bolts and disconnecting the connector.
• Remove the spark plug using a spark plug socket.
• Inspect the spark plug for wear, carbon buildup, or damage. Replace with a new spark plug if necessary, ensuring it meets OEM specifications.
• Reinstall the spark plug and torque to the manufacturer’s specifications (typically around 22 ft-lbs).

3. Inspect and Replace Ignition Coil

• If the spark plug is in good condition, proceed to the ignition coil.
• Remove the ignition coil from cylinder 1.
• Test the ignition coil using a multimeter; if out of specification, replace it with a new one.
• Reinstall the ignition coil and ensure it is seated properly.

4. Test Fuel Injector

• If the ignition components are functioning, test the fuel injector for cylinder 1.
• Disconnect the fuel injector connector and use a noid light to confirm it is receiving a signal.
• If not receiving a signal, inspect wiring and connectors for damage. If the injector is faulty, replace it with a new one.

5. Check for Vacuum Leaks

• Inspect all vacuum hoses and connections around the intake manifold for cracks or disconnections.
• Use a smoke machine or carburetor cleaner to identify leaks. Repair or replace any damaged hoses.