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

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Disconnect the battery to prevent electrical shorts.

2. Replace Spark Plug

• Tools Needed: Spark plug socket, ratchet, torque wrench
• Remove the ignition coil by unscrewing any bolts and disconnecting the electrical connector.
• Remove the old spark plug using a spark plug socket and inspect for damage or excessive wear.
• Install a new spark plug (ensure it is the correct type and gap is set according to manufacturer specifications).
• Torque the spark plug to the specified value (typically around 23 Nm).
• Reinstall the ignition coil and reconnect the electrical connector.

3. Replace Ignition Coil (if necessary)

• If the ignition coil was found faulty during diagnostics, replace it.
• Remove the faulty ignition coil as described above.
• Install the new ignition coil and ensure it is securely seated and connected.

4. Inspect/Replace Fuel Injector (if necessary)

• Tools Needed: Fuel injector puller (if necessary), O-ring lubricant
• Disconnect the fuel line and electrical connector from the fuel injector.
• Remove the fuel injector from the rail (note any O-rings and seals).
• Inspect the injector for clogs or damage; replace if necessary.
• Lubricate new O-rings with engine oil and install the new fuel injector.
• Reconnect the fuel line and electrical connector securely.

5. Perform a Compression Test (if misfire persists)

• If replacing the spark plug, ignition coil, and fuel injector does not resolve the issue, conduct a compression test.
• Remove the spark plugs and attach the compression gauge to cylinder 1.
• Crank the engine and record the compression reading.
• Compare it to manufacturer specifications (typically around 120-150 psi for most engines); low compression indicates deeper engine issues.