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

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Replace Spark Plug

• Tools Required: Socket set, torque wrench, spark plug socket.
• Remove the engine cover if applicable.
• Disconnect the ignition coil connector and remove the ignition coil from cylinder 1.
• Use a spark plug socket to remove the spark plug from cylinder 1.
• Inspect the spark plug for signs of wear or fouling. If damaged, replace it with a new spark plug, ensuring it meets OEM specifications.
• Torque the new spark plug to the manufacturer’s specification, typically around 22 lb-ft (30 Nm).

3. Check and Replace Ignition Coil

• If the spark plug is fine, test the ignition coil by swapping it with a working coil from another cylinder.
• Reconnect the ignition coil and test run the engine.
• If the misfire persists, replace the ignition coil with a new one that meets OEM standards.

4. Inspect and Test Fuel Injector

• Use a multimeter to check the resistance of the fuel injector connected to cylinder 1. It should typically read between 12-16 ohms.
• If the reading is outside this range, replace the fuel injector.
• For testing, you may also use a noid light to check for proper signal to the injector.

5. Check for Vacuum Leaks

• Inspect all vacuum hoses and the intake manifold for cracks or disconnections.
• Use a smoke machine or carburetor cleaner to identify leaks by observing changes in idle speed.
• Repair or replace any damaged hoses or gaskets.