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

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Ensure the vehicle is parked on a flat surface with the engine turned off and cooled down.

2. Replace Spark Plug

• Tools Required: Spark plug socket, ratchet, torque wrench.
• Remove the engine cover if necessary.
• Disconnect the ignition coil connector for cylinder 1.
• Unscrew the ignition coil and remove it from the spark plug.
• Use the spark plug socket to remove the old spark plug.
• Inspect the new spark plug for proper gap and install it into the cylinder head, hand-tightening it first.
• Torque the spark plug to manufacturer specifications (usually around 20 Nm / 15 lb-ft).
• Reinstall the ignition coil and connect the electrical connector securely.

3. Inspect and Replace Ignition Coil

• If the spark plug replacement does not resolve the issue, proceed to the ignition coil.
• Remove the ignition coil from cylinder 1 (as detailed in step 2).
• Test the ignition coil with a multimeter (check primary and secondary resistance) according to specifications.
• If faulty, replace the ignition coil with a new one, ensuring it matches the part number.
• Reconnect the ignition coil connector once installed.

4. Clean or Replace Fuel Injector

• If the misfire persists, check the fuel injector.
• Disconnect the fuel injector connector for cylinder 1.
• Remove the fuel rail if necessary to access the injector.
• Clean the injector using a fuel injector cleaning kit or replace it if it is clogged or malfunctioning.
• Reinstall the fuel rail and reconnect all connectors.

5. Conduct Compression Test

• If all previous steps do not solve the issue, perform a compression test on cylinder 1.
• Remove the spark plug and insert the compression gauge in the spark plug hole.
• Crank the engine and record the compression reading.
• If the compression is below the manufacturer's specifications, further investigation into internal engine issues may be required.